Stone to Grain Converter
Convert stones to grains with our free online weight converter.
Quick Answer
1 Stone = 98000 grains
Formula: Stone × conversion factor = Grain
Use the calculator below for instant, accurate conversions.
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All conversion formulas on UnitsConverter.io have been verified against NIST (National Institute of Standards and Technology) guidelines and international SI standards. Our calculations are accurate to 10 decimal places for standard conversions and use arbitrary precision arithmetic for astronomical units.
Stone to Grain Calculator
How to Use the Stone to Grain Calculator:
- Enter the value you want to convert in the 'From' field (Stone).
- The converted value in Grain will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Weight category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Stone to Grain: Step-by-Step Guide
Converting Stone to Grain involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Stone = 98000 grainsExample Calculation:
Convert 5 stones: 5 × 98000 = 490000 grains
Disclaimer: For Reference Only
These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.
Not for professional use. Results should be verified before use in any critical application. View our Terms of Service for more information.
Need to convert to other weight units?
View all Weight conversions →What is a Stone and a Grain?
1 stone = 14 avoirdupois pounds (lb) = 6.35029318 kilograms (kg) EXACT
The stone (symbol: st) is a unit of mass in the Imperial system, legally defined in terms of pounds, which are themselves defined in terms of kilograms. The exact conversion is:
1 pound = 0.45359237 kilograms (international definition, 1959)
1 stone = 14 × 0.45359237 kg = 6.35029318 kg
Stone and Pounds Notation
The stone is almost never used alone for body weight. Instead, it's combined with additional pounds:
Format: "X stone Y pounds" or "X st Y lb"
Examples:
- 10 st 0 lb = 10 stone exactly = 140 lb = 63.5 kg
- 10 st 7 lb = 10 stone + 7 pounds = 147 lb = 66.7 kg
- 12 st 3 lb = 12 stone + 3 pounds = 171 lb = 77.6 kg
Why this format? It provides precision without unwieldy decimal places. Saying "10.5 stone" is rare—people say "10 stone 7" instead (10 stone + 7 pounds = 10.5 stone).
Stone vs. Kilogram vs. Pound
Three systems for measuring body weight:
| System | Unit | Used In | Precision | |-----------|----------|-------------|---------------| | Imperial (UK) | Stone + Pounds | UK, Ireland | "11 st 7 lb" (161 lb) | | Imperial (US) | Pounds only | United States, Canada | "161 lb" | | Metric | Kilograms | Most of the world | "73 kg" |
Cultural difference:
- Americans say "I weigh 161 pounds"
- British say "I weigh 11 stone 7" (rarely "161 pounds")
- Europeans say "I weigh 73 kilograms"
Why 14 Pounds?
The number 14 has no scientific basis—it's purely historical. Medieval England used base-12 counting (duodecimal) for some systems:
- 12 inches = 1 foot
- 12 pence = 1 shilling (pre-1971)
- But 14 pounds = 1 stone (not 12!)
Theory: The 14-pound wool stone emerged from trade practices. A "sack of wool" weighed 364 pounds = 26 stones (26 × 14 = 364), a convenient round number for taxation and commerce.
1 grain = 64.79891 milligrams (mg) = 0.06479891 grams (g) EXACT
The grain (symbol: gr) is a unit of mass legally defined since 1959 as exactly 64.79891 milligrams. It is the smallest and oldest unit in the traditional English measurement systems.
Grain in Three Weight Systems
The grain is unique—it's the only unit shared identically across three different weight systems:
| System | Use | Grain Relationships | |-----------|---------|------------------------| | Avoirdupois | General commerce, bullets | 437.5 gr = 1 oz; 7,000 gr = 1 lb | | Troy | Precious metals, gemstones | 480 gr = 1 oz troy; 5,760 gr = 1 lb troy | | Apothecaries' | Pharmacy (historical) | 480 gr = 1 oz apoth; 5,760 gr = 1 lb apoth |
Why this matters: The grain serves as the common denominator linking these systems. It's the conversion bridge between everyday weights and specialized applications.
The Barleycorn Origin
Historical basis: The grain was originally defined as the weight of a single grain of barley taken from the middle of the ear (not from the ends, which are lighter).
Remarkably consistent: Medieval experiments showed barleycorns have remarkably uniform mass:
- Average: 64-66 milligrams
- Modern definition: 64.79891 mg
- Variance: Only ~2-3% across different barley varieties
Length connection: King Edward I's statute (13th century) also defined 1 inch = 3 barleycorns laid end-to-end. Thus, the barleycorn defined both length and weight!
Metric Equivalents
Precise conversion:
1 grain = 64.79891 milligrams (EXACT, since 1959)
Common approximations:
1 grain ≈ 0.0648 grams (rounded)
1 grain ≈ 65 milligrams (rough)
15.43 grains ≈ 1 gram (useful for quick conversions)
Why 64.79891 mg? This exact value comes from the 1959 international yard and pound agreement:
- 1 pound = 0.45359237 kg (defined)
- 1 grain = 1/7000 pound
- 1 grain = 0.45359237 ÷ 7000 = 0.00006479891 kg = 64.79891 mg
Note: The Stone is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Grain belongs to the imperial/US customary system.
History of the Stone and Grain
Ancient and Medieval Origins (Pre-1300)
The concept of standardized stones: Before precise metallic weights, communities used stones as trade counterweights. A merchant would keep a reference stone in the marketplace, verified by local authorities, against which goods were weighed.
Advantages:
- Durability: Stones don't corrode or wear like metal
- Availability: Every village had stones
- Tamper-resistance: Hard to secretly shave weight off a stone
Problem: Every region had different stones! The "stone of wool" in Yorkshire differed from the "stone of wool" in Kent.
Medieval Standardization Attempts (1300-1824)
Edward III's wool stone (1340): King Edward III standardized the wool stone at 14 pounds as part of regulating the lucrative wool trade (England's economic backbone in the Middle Ages). The "sack of wool" was defined as 364 pounds = 26 stones.
Commodity-specific stones: Different goods had different stone weights:
| Commodity | Stone Weight | Reasoning | |--------------|-----------------|---------------| | Wool | 14 lb (6.35 kg) | Trade standard | | Meat | 8 lb (3.63 kg) | Butcher's stone | | Glass | 5 lb (2.27 kg) | Fragile goods | | Cheese | 16 lb (7.26 kg) | Agricultural products | | Iron | Variable (8-15 lb) | Regional differences |
Why different weights? Practical reasons:
- Heavy commodities (iron, lead): Smaller stone weight made counting easier
- Light, valuable goods (wool, spices): Larger stone weight reduced fractions
- Tradition: Each guild jealously guarded its customary weights
The Weights and Measures Act 1824
The problem: By 1800, Britain had dozens of incompatible stone definitions, creating chaos in trade and taxation.
The solution: The 1824 Act standardized British weights and measures:
- 14 pounds = 1 stone (for general use, not tied to specific commodities)
- Stone officially defined in relation to the pound
- Commodity-specific stones discouraged (but not banned)
Imperial standardization: The Act also defined:
- 1 pound = 7,000 grains
- 16 ounces = 1 pound
- 14 pounds = 1 stone
- 8 stone = 1 hundredweight (112 pounds)
- 20 hundredweight = 1 ton (2,240 pounds)
Body weight adoption: The Victorian era (1837-1901) saw the stone become the standard for human weighing. Bathroom scales, medical records, and public health data used stones and pounds.
Metrication and Persistence (1965-Present)
The Weights and Measures Act 1965: The UK officially adopted the metric system, making kilograms the legal unit for trade. However, the Act exempted personal weighing—bathroom scales could continue showing stones.
Why the exemption?
- Cultural resistance: Brits refused to abandon stones for body weight
- Economic lobbying: Scale manufacturers didn't want to retool
- Medical inertia: NHS records already used stones; conversion would be costly
The result: 60+ years later, the stone persists:
- Bathroom scales: Default to stones in the UK (even modern digital ones)
- NHS medical records: Still record patient weight in stones/pounds
- Weight loss programs: Slimming World, Weight Watchers UK use stones
- Media: British newspapers report celebrity weight in stones
- Sports: Boxing, horse racing, rowing use stones for weight classes
Ireland's experience: Ireland officially adopted metric units in 2005, but the stone remains common for body weight, especially among older generations.
Generational divide:
- Older Brits (60+): Think exclusively in stones
- Middle-aged (30-60): Bilingual (stones and kilograms)
- Younger (<30): Increasingly use kilograms, but still understand stones
Cultural Tenacity
The stone is the most persistent Imperial unit in British daily life, outlasting:
- Fahrenheit: Replaced by Celsius (weather, ovens)
- Inches/feet for height: Partially replaced by metres (though feet still common)
- Pints: Milk sold in litres (though beer still sold in pints!)
- Miles: Road signs still use miles (the UK never fully switched)
Why the stone survives:
- Emotional connection: Body weight is personal; changing units feels invasive
- Convenient range: For adults, weight is 8-20 stones (easy to remember vs. 50-127 kg)
- Medical exemption: Doctors use stones, so patients use stones
- Social reinforcement: Everyone around you uses stones, so you do too
Ancient Origins (3000 BCE - 500 CE)
Mesopotamian seeds: The earliest weight systems in Sumer and Babylon (circa 3000-2000 BCE) used seeds as counterweights:
- Barleycorns: Small weights
- Wheat grains: Alternative standard
- Carob seeds: Larger weights (origin of "carat" for gemstones)
Why seeds? Seeds have several advantages as weights:
- Availability: Every agricultural community had grain
- Uniformity: Grains from the same species have consistent mass
- Portability: Easy to carry, store, and count
- Natural standard: Self-evident, no authority needed to verify
Babylonian system:
- 180 barleycorns = 1 shekel (~8.4 grams)
- Shekels formed the basis for Mesopotamian commerce
Egyptian weights: Ancient Egypt used wheat grains similarly, though their system developed independently.
Greek and Roman Adoption (500 BCE - 500 CE)
Roman grain (granum): Romans used grains of wheat as small weight standards:
- 1 siliqua (carob seed) = 3 grains of wheat
- 24 siliquae = 1 solidus (Roman gold coin, ~4.5 grams)
Classical pharmacy: Greek and Roman physicians (Hippocrates, Galen) prescribed medicines in grain weights, establishing the apothecaries' tradition.
Medieval England (1000-1500 CE)
Barleycorn statutes: English law formalized the barleycorn as both length and weight standard.
King Edward I (1272-1307): His statute defined:
- 1 inch = 3 barleycorns laid end-to-end
- 1 grain = weight of 1 barleycorn from the middle of the ear
Establishing the pound: The avoirdupois pound was defined as 7,000 grains, making the grain the fundamental unit.
Why 7,000? Likely evolved from trade practices. 7,000 is divisible by many numbers (1, 2, 4, 5, 7, 8, 10, 14, 20, etc.), making fractional calculations easier.
Troy vs. Avoirdupois:
- Troy pound: 5,760 grains (12 troy ounces × 480 grains)
- Avoirdupois pound: 7,000 grains (16 avoirdupois ounces × 437.5 grains)
- Grain: Identical in both systems (the common unit)
Gunpowder and Firearms (1300-1800)
Black powder measurement: The invention of gunpowder (China, 9th century; Europe, 13th century) required precise measurement. Early gunners measured powder charges in grains for consistency.
Why grains for gunpowder?
- Precision: Small unit allows fine-tuning of powder charges
- Safety: Overcharging a cannon or musket could cause explosion
- Consistency: Uniform charges improve accuracy
Development of firearms: As firearms evolved from cannons to muskets to rifles (1400s-1800s), grain measurement became standard:
- Musket ball: 400-500 grains (26-32 grams)
- Powder charge: 70-100 grains (4.5-6.5 grams)
Ballistics science: By the 18th century, ballistics became a science, with detailed tables relating bullet weight (grains), powder charge (grains), and muzzle velocity.
Apothecaries' and Pharmacy (1500-1900)
Apothecaries' system: Pharmacists adopted the grain from medieval medicine, using it alongside drams, scruples, and ounces.
System structure:
- 20 grains = 1 scruple
- 3 scruples = 1 dram
- 8 drams = 1 ounce (apothecaries')
- 12 ounces = 1 pound (apothecaries')
Why grains for medicine?
- Precision: Many drugs are potent at milligram doses (grain scale)
- Safety: Overdosing could be fatal; grains allowed careful measurement
- Tradition: Galen, Hippocrates used grains; continuity mattered
Common medications:
- Aspirin: 5 grains (325 mg) — "standard dose"
- Morphine: 1/4 to 1 grain (16-65 mg) — pain relief
- Digitalis: 1/60 to 1/30 grain (1-2 mg) — heart medication
Modern Standardization (1900-Present)
The 1959 Agreement: The international yard and pound agreement fixed the grain:
- 1 pound = 0.45359237 kilograms (EXACT)
- 1 grain = 1/7000 pound = 64.79891 mg (EXACT)
This ended slight variations between British and US grains.
Metrication in pharmacy: Most countries switched to milligrams for drug dosing (1950s-1980s). However:
- United States: Some medications retain grain labels (aspirin, thyroid hormone)
- UK: Fully metric in pharmacy by 1970s
Persistence in ammunition: Unlike pharmacy, the ammunition industry never metricated:
- US ammunition: Grains (dominant globally)
- European ammunition: Some metric (grams), but grains still common for export
Modern shooting sports: Competitive shooting, reloading, and ballistics all use grains:
- Bullet weight: Grains
- Powder charge: Grains
- Arrow weight: Grains (archery)
Common Uses and Applications: stones vs grains
Explore the typical applications for both Stone (imperial/US) and Grain (imperial/US) to understand their common contexts.
Common Uses for stones
1. Body Weight Measurement
The stone is the unit for body weight in the UK and Ireland.
Bathroom scales:
- Display: "11 st 7 lb" (digital) or analog dial with stone markings
- Dual units: Many scales toggle between st/lb and kg
- Default: Stones for UK-sold scales, even from international brands
Weighing yourself:
- British: "I'm 12 stone 3"
- American: "I'm 171 pounds"
- European: "I'm 78 kilograms"
Weight goals:
- "I want to lose a stone" = 14-pound goal
- "I'm aiming for 10 stone" = target weight
- "I've gained half a stone" = 7-pound increase
2. Medical and Healthcare
NHS patient records: British hospitals and GPs record weight in stones/pounds (with kg conversion).
Medical forms:
- Pre-op questionnaires: "Weight: __ st __ lb"
- Prescription dosing: Sometimes based on weight (converted to kg for calculations)
- Anesthesia planning: Weight in stones converted to kg for drug dosages
Maternity care:
- Booking appointment: "What was your pre-pregnancy weight?" (stones)
- Pregnancy weight tracking: "You've gained 2 stone, which is healthy"
- Post-natal: "Most women lose 1-2 stone in the first weeks"
Mental health context: Eating disorder treatment tracks weight changes in stones (e.g., anorexia recovery: "gained 1 stone to 7 stone 10").
3. Weight Loss and Fitness
Slimming clubs:
- Slimming World, Weight Watchers UK: Weigh-ins in stones
- Awards: "Half-stone hero," "Stone club," "3-stone milestone"
- Targets: "Lose 10% of body weight" (e.g., 1.5 stone from 15 stone start)
Fitness apps (UK versions):
- MyFitnessPal UK: Input weight in stones
- Fitbit/Garmin: UK users set goals in stones
- Weight tracking graphs: Y-axis shows stones, not kg
Personal trainers: British trainers discuss client progress in stones: "You've dropped from 14 stone to 12 stone 8—fantastic!"
4. Sports Weight Classes
Boxing: British boxing traditionally used stones for weight classes (now officially kilograms, but stones still common in commentary).
Horse racing:
- Jockey weights: Includes jockey + saddle + lead weights to meet required "riding weight"
- Handicapping: Horses carry different weights (in stones) to equalize competition
- Penalties: "Carrying 9 stone 7" vs. "Carrying 10 stone" affects race outcomes
Rowing: Lightweight rowers must weigh under certain stone limits (now metric, but historically stones).
5. Everyday Conversation
The stone pervades British informal speech:
Common phrases:
- "I'm 11 stone, give or take" = approximate weight
- "She must be 10 stone soaking wet" = very light
- "He's put on a stone since Christmas" = seasonal weight gain
- "I haven't been 9 stone since I was 15!" = nostalgic reference
Social etiquette:
- It's impolite to ask someone's weight directly, but acceptable to discuss your own
- Women might say "I'm trying to get back to 9 stone" (goal weight)
6. Media and Entertainment
British TV shows:
- Reality TV: "Love Island" contestants' weights discussed in tabloids (stones)
- Medical shows: "Embarrassing Bodies" references patient weight in stones
- Game shows: "The Biggest Loser UK" tracked loss in stones
Newspapers and magazines:
- Celebrity weight speculation: "Has she lost 2 stone?"
- Health articles: "How to lose half a stone by summer"
- Success stories: "I lost 8 stone and transformed my life!"
7. Historical and Cultural References
Literature: Victorian novels reference weight in stones:
- Dickens, Austen rarely mention specific weights (impolite)
- 20th-century literature: "She was a strapping girl of 12 stone"
British humor: Comedians joke about weight in stones:
- "I'm not overweight, I'm just undertall for my 14 stone!"
Generational markers:
- Older Brits: "When I got married, I was 8 stone"
- Modern comparison: "That's only 112 pounds—too thin by today's standards!"
When to Use grains
1. Ammunition Manufacturing and Reloading
The grain is the universal standard for bullet and powder measurement.
Bullet weight: Every ammunition box lists bullet weight in grains:
- 9mm: "115 gr FMJ" = 115-grain full metal jacket
- .308: "168 gr HPBT" = 168-grain hollow-point boat-tail
Powder charges: Reloaders measure powder in grains using precision scales:
- Typical pistol charge: 3-10 grains
- Typical rifle charge: 20-60 grains
Why grains persist:
- Ballistics tables: Decades of data in grains
- Reloading manuals: All recipes in grains
- International standard: Even metric countries use grains for export ammo
- Precision: Grain scale appropriate for small differences that matter
2. Archery
Arrow selection: Archers match arrow weight (grains) to bow draw weight:
- Too light: Bow damage risk
- Too heavy: Poor trajectory
Broadheads: Hunting broadheads sold by weight:
- 75 grain, 100 grain, 125 grain, etc.
Tuning: Archers adjust arrow weight by changing point weight (grains) to fine-tune flight.
3. Pharmaceuticals (Historical and Residual)
United States: Some medications still list grain dosages:
- Aspirin: 5 grain (325 mg)
- Thyroid medication: Grain equivalents
Medical history: Understanding grain dosages important for:
- Historical medical research
- Old prescriptions
- Classic pharmaceutical formulations
4. Jewelry and Precious Metals
Troy system: Grains underpin the troy weight system used for gold, silver, platinum.
Jeweler's usage:
- Weighing scrap: Pennyweights (24 grains)
- Gold purity calculations: Grain-based math
- Stone setting: Small gemstones sometimes measured in grains
5. Historical and Collectors' Context
Numismatics (coin collecting): Historical coins' weights recorded in grains:
- Helps identify counterfeits (wrong weight)
- Documents wear (lost grains over time)
Antique firearms: Black powder firearms measured in grains:
- "This musket took 90 grains of powder and a 450-grain ball"
6. Scientific and Educational
Teaching weight systems: The grain demonstrates the connection between avoirdupois, troy, and apothecaries' systems.
Historical science: Understanding old experiments and recipes requires grain knowledge:
- 18th-century chemistry
- Medieval alchemy
- Renaissance medicine
7. International Trade
Ammunition export: US and European manufacturers use grains globally:
- 124 gr 9mm NATO standard (worldwide)
- Even metric-preferring countries import grain-labeled ammo
Additional Unit Information
About Stone (st)
1. How many pounds are in a stone?
Exactly 14 pounds.
This is a defined constant. There are no regional variations—1 stone always equals 14 pounds in any context.
Calculation examples:
- 5 stone = 5 × 14 = 70 pounds
- 12 stone = 12 × 14 = 168 pounds
- 0.5 stone = 0.5 × 14 = 7 pounds
2. Is the stone used outside the UK and Ireland?
Rarely. The stone is almost exclusive to the UK and Ireland.
Usage by country:
- UK: Dominant for body weight (even with official metrication)
- Ireland: Common, especially among older generations
- Canada, Australia, New Zealand: Not used (fully metric)
- United States: Not used (pounds only)
- Rest of world: Not used (metric)
Exception: British expats abroad sometimes use stones, and international weight loss forums may reference stones when discussing UK participants.
3. Why is it called a stone?
Historical practice: Actual stones were used as standardized weights in medieval markets.
How it worked:
- A community selected a reference stone of agreed weight
- The stone was kept in the marketplace (sometimes literally built into a wall)
- Merchants used the reference stone on balance scales to verify weights
- Different stones existed for different commodities (wool stone, meat stone, etc.)
Modern name: The unit name "stone" is a fossil of this practice, long after actual stones stopped being used.
4. How do you convert stone to kilograms?
Formula:
Kilograms = Stone × 6.35029318
Quick approximation:
Kilograms ≈ Stone × 6.35 (good to 3 decimal places)
Examples:
- 10 stone × 6.35 = 63.5 kg
- 12 stone × 6.35 = 76.2 kg
- 15 stone × 6.35 = 95.25 kg
Online tools: Most conversion sites and apps include stone ↔ kilogram calculators.
5. How do British people talk about their weight?
Typical format: "I'm X stone Y pounds" or "I'm X stone Y"
Examples:
- "I'm 11 stone 7" = 11 stone + 7 pounds = 161 lb = 73 kg
- "I'm just over 12 stone" = slightly more than 168 lb
- "I'm nearly 10 stone" = approaching 140 lb
Rarely said:
- "I'm 11.5 stone" (uncommon—people say "11 stone 7" instead)
- "I'm 161 pounds" (too American—Brits don't think in pounds alone)
- "I'm 73 kilograms" (used by younger generations, but less common)
Conversational weight: Discussing weight is somewhat taboo, so people often avoid specifics: "I need to lose a bit of weight" rather than "I need to drop from 13 to 11 stone."
6. Do British bathroom scales show kilograms?
Yes, most modern scales show both.
Typical features:
- Default: Stones and pounds (st/lb)
- Toggle button: Switch to kilograms
- Dual display: Some show both simultaneously
Older scales: Analog scales from before 2000 often show stones only.
Buying scales in the UK: Even international brands (Fitbit, Garmin) sell UK-specific versions that default to stones.
7. Will the UK ever stop using stones?
Unlikely in the near future.
Reasons for persistence:
- Cultural attachment: Body weight is personal; people resist change
- Legal exemption: Personal weighing scales exempt from trade regulations
- NHS inertia: Changing medical records costly
- Generational use: Older generations use stones exclusively
- No enforcement: No push to mandate kilograms for personal use
Trend: Younger Brits (under 30) increasingly use kilograms, especially those who travel or use fitness apps with international audiences. However, the stone will likely persist for decades among older populations.
Comparison: Similar to Fahrenheit in the US—officially discouraged but culturally entrenched.
8. What is a "half stone"?
Half stone = 7 pounds = 3.175 kg
Usage:
- Weight loss: "I've lost half a stone" = 7 lb loss
- Weight gain: "I've put on half a stone over Christmas" = 7 lb gain
- Milestones: "Half-stone club" in weight loss programs
Why significant? Half a stone is a noticeable weight change—enough to affect how clothes fit and how you feel, but achievable in 3-7 weeks of dieting (at 1-2 lb/week loss).
9. How do you write stone and pounds?
Common formats:
Formal:
- "11 stone 7 pounds"
- "11 st 7 lb"
Informal:
- "11 stone 7"
- "11st 7lb" (no spaces)
- "11-7" (very casual, context-dependent)
Avoid:
- "11.7 stone" (ambiguous—could mean 11 stone 7 lb or 11 stone 9.8 lb)
- "11/7 st" (confusing notation)
Medical records: NHS typically uses "st/lb" format: "Patient weight: 12 st 3 lb"
10. Why do Americans not use stone?
The United States never adopted the stone for body weight.
Historical reasons:
- Colonial divergence: By the time the stone standardized in Britain (1824), the US had already established pounds as the body weight unit
- Decimal preference: Americans favored simpler base-10 systems where possible
- No cultural push: No equivalent to UK's Victorian-era adoption of stones for weighing people
Result: Americans think in pounds only:
- "I weigh 180 pounds" (no stones)
- Weight loss: "I lost 30 pounds" (not "2 stone 2 pounds")
Canadian note: Canada officially metricated in the 1970s and uses kilograms, not stones or pounds (though older Canadians may still think in pounds).
11. Is stone a legal unit?
Yes, in the UK and Ireland, but with restrictions.
Legal status:
- Personal use: Fully legal (bathroom scales, self-weighing)
- Trade: Must use metric (kilograms) for selling goods by weight
- Medical: Allowed in patient records (NHS uses stones)
Weights and Measures Act: Kilograms are the legal unit for commerce, but stones remain legal for "non-trade" purposes (personal weighing, medical records).
Comparison: Similar to miles on UK road signs—officially metric, but exceptions preserve traditional units in specific contexts.
12. How much is a stone in other historical weight units?
Stone in troy and apothecary systems:
Troy weight (precious metals):
- 1 stone (avoirdupois) = 14 pounds (avoirdupois)
- 1 pound (avoirdupois) = 7,000 grains
- 1 stone = 98,000 grains (troy)
- 1 troy pound = 5,760 grains
- 1 stone ≈ 17.01 troy pounds
Apothecaries' weight (pharmacy):
- Same grain as troy and avoirdupois (64.79891 mg)
- 1 stone = 98,000 grains (apothecaries')
Why this matters: Historically, pharmacists used apothecaries' weights, so understanding stone conversions was important for dosing medicines based on body weight.
About Grain (gr)
1. How many grains are in an ounce (avoirdupois)?
Exactly 437.5 grains.
This is a defined relationship in the avoirdupois system:
- 1 pound (avoirdupois) = 7,000 grains
- 1 pound = 16 ounces
- 1 ounce = 7,000 ÷ 16 = 437.5 grains
2. How many grains are in a pound (avoirdupois)?
Exactly 7,000 grains.
The avoirdupois pound is defined as 7,000 grains. This is the legal definition in both US and UK systems (since the 1959 international agreement).
Example: A 1-pound bag of bullets contains 7,000 grains of lead.
3. How many milligrams are in a grain?
Exactly 64.79891 milligrams.
This precise value comes from:
- 1 pound = 453.59237 grams (defined, 1959)
- 1 grain = 1/7000 pound
- 1 grain = 453.59237 ÷ 7000 = 0.06479891 g = 64.79891 mg
4. Why is ammunition measured in grains instead of grams?
Historical precedent and global standardization.
Reasons:
- Ballistics data: Centuries of data in grains (velocity, energy, trajectory)
- Reloading manuals: All powder recipes in grains
- International standard: Even metric countries export ammo labeled in grains
- Precision: Grain scale (65 mg) well-suited for bullet weights (2-50 grams)
- Continuity: Changing would require recalibrating every firearm manual and table
Result: The shooting industry worldwide uses grains, regardless of country.
5. Is a grain the same in troy, avoirdupois, and apothecaries' systems?
Yes, exactly the same.
The grain is the only unit shared identically across all three systems:
- 1 grain (avoirdupois) = 64.79891 mg
- 1 grain (troy) = 64.79891 mg
- 1 grain (apothecaries') = 64.79891 mg
Why this matters: The grain is the common denominator, allowing conversion between systems.
Example:
- 480 grains = 1 troy ounce = 1 apothecaries' ounce
- 437.5 grains = 1 avoirdupois ounce (different!)
6. How many grains are in a gram?
Approximately 15.43236 grains.
Formula:
1 gram = 1,000 mg
1 grain = 64.79891 mg
1 gram = 1,000 ÷ 64.79891 = 15.43236 grains
Quick approximation: 1 gram ≈ 15.4 grains (useful for mental math)
7. What does "5 grain aspirin" mean?
A tablet containing 5 grains of aspirin = 325 milligrams.
Calculation:
5 grains × 64.79891 mg/grain = 323.99 mg ≈ 325 mg
Why 325 mg tablets? Historical: Aspirin was formulated in grain dosages. When pharmacy metricated, 5 grains became 325 mg (rounded for convenience).
8. How much does a barleycorn actually weigh?
About 50-70 milligrams, depending on variety.
Modern grain vs. actual barleycorn:
- Defined grain: 64.79891 mg (EXACT)
- Actual barleycorn: 50-70 mg (varies)
Remarkably close! Medieval barleycorns averaged ~65 mg, very close to the modern definition.
Why the difference today? The grain is now a defined constant, not dependent on actual barley. This ensures global consistency.
9. Why is the grain 1/7000 of a pound?
Historical evolution, not mathematical planning.
Theory: The pound and grain evolved separately:
- Grain: Ancient seed weight
- Pound: Medieval trade weight
The 7,000-grain pound emerged from trade practices and was standardized by law (13th-14th century England).
Convenience: 7,000 is highly divisible (1, 2, 4, 5, 7, 8, 10, 14, 20, 25, 28, 35, 40, 50, 56, 70, 100, 125, 140, 175, 200, 250, 280, 350, 500, 700, 1000, 1400, 1750, 2333, 3500, 7000), making fractional calculations easier in pre-calculator commerce.
10. Do other countries use grains?
Yes, for ammunition and archery worldwide.
By country:
- United States: Grains for ammo, archery, some pharmaceuticals
- United Kingdom: Grains for ammo, archery (pharmacy now metric)
- Europe: Grains for ammunition exports, some domestic ammo
- Asia, Australia: Grains for ammunition, archery
Pharmaceutical use: Mostly obsolete outside the U.S. (switched to milligrams).
Why grains persist globally: Ammunition is an international market. Standardization on grains ensures compatibility.
11. How accurate do reloading scales need to be?
±0.1 grain (±0.0065 grams) minimum.
Why such precision?
- Small powder charges: 3-10 grains (pistol), 20-60 grains (rifle)
- ±0.1 grain = ±1-3% variation (acceptable)
- ±1 grain = ±10-30% variation (dangerous!)
Scale types:
- Beam balance: Manual, ±0.1 grain typical
- Digital: Electronic, ±0.1 grain or better
- Trickler: Adds powder grain-by-grain for exactness
Safety: Reloading is unforgiving. Precision scales are essential to avoid overpressure, case ruptures, or injuries.
12. What is the relationship between grain and carat?
1 carat (gemstone) = 200 milligrams = 3.086 grains.
Calculation:
1 carat = 200 mg
1 grain = 64.79891 mg
1 carat = 200 ÷ 64.79891 = 3.086 grains
Historical connection: Both derive from seeds:
- Grain: Barleycorn
- Carat: Carob seed (~200 mg)
Modern difference:
- Carat: Used for gemstones (diamonds, rubies, sapphires)
- Grain: Used for bullets, arrows, pharmaceuticals
Overlap: Small gemstones or pearls historically measured in grains; now almost exclusively carats.
Conversion Table: Stone to Grain
| Stone (st) | Grain (gr) |
|---|---|
| 0.5 | 49,000 |
| 1 | 98,000 |
| 1.5 | 147,000 |
| 2 | 196,000 |
| 5 | 490,000 |
| 10 | 980,000 |
| 25 | 2,450,000 |
| 50 | 4,900,000 |
| 100 | 9,800,000 |
| 250 | 24,500,000 |
| 500 | 49,000,000 |
| 1,000 | 98,000,000 |
People Also Ask
How do I convert Stone to Grain?
To convert Stone to Grain, enter the value in Stone in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our weight converter page to convert between other units in this category.
Learn more →What is the conversion factor from Stone to Grain?
The conversion factor depends on the specific relationship between Stone and Grain. You can find the exact conversion formula and factor on this page. Our calculator handles all calculations automatically. See the conversion table above for common values.
Can I convert Grain back to Stone?
Yes! You can easily convert Grain back to Stone by using the swap button (⇌) in the calculator above, or by visiting our Grain to Stone converter page. You can also explore other weight conversions on our category page.
Learn more →What are common uses for Stone and Grain?
Stone and Grain are both standard units used in weight measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our weight converter for more conversion options.
For more weight conversion questions, visit our FAQ page or explore our conversion guides.
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⚖️ Metric vs Imperial
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Other Weight Units and Conversions
Explore other weight units and their conversion options:
- Kilogram (kg) • Stone to Kilogram
- Gram (g) • Stone to Gram
- Milligram (mg) • Stone to Milligram
- Pound (lb) • Stone to Pound
- Ounce (oz) • Stone to Ounce
- Ton (metric) (t) • Stone to Ton (metric)
- Ton (US) (ton) • Stone to Ton (US)
- Ton (UK) (long ton) • Stone to Ton (UK)
- Microgram (µg) • Stone to Microgram
- Carat (ct) • Stone to Carat
Verified Against Authority Standards
All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.
National Institute of Standards and Technology — US standards for weight and mass measurements
International Organization for Standardization — International standard for mechanics quantities
Last verified: February 19, 2026