Yard to Parsec Converter
Convert yards to parsecs with our free online length converter.
Quick Answer
1 Yard = 2.963347e-17 parsecs
Formula: Yard × conversion factor = Parsec
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.
Yard to Parsec Calculator
How to Use the Yard to Parsec Calculator:
- Enter the value you want to convert in the 'From' field (Yard).
- The converted value in Parsec will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Length category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Yard to Parsec: Step-by-Step Guide
Converting Yard to Parsec involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Yard = 2.9633e-17 parsecsExample Calculation:
Convert 10 yards: 10 × 2.9633e-17 = 2.9633e-16 parsecs
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 length units?
View all Length conversions →What is a Yard and a Parsec?
The yard is a unit of length in the British imperial and United States customary systems of measurement. It is defined as exactly 3 feet or 36 inches, which equals 0.9144 meters.
Precise definition:
- 1 yard = 3 feet (exactly)
- 1 yard = 36 inches (exactly)
- 1 yard = 0.9144 meters (exactly, since 1959)
- 1 yard = 91.44 centimeters
- 1 yard = 914.4 millimeters
Relationship to other units:
- 1 meter = 1.09361 yards (about 9.4% longer)
- 1 mile = 1,760 yards
- 1 furlong = 220 yards
- 1 rod = 5.5 yards
Yard vs. Meter: Key Comparison
This is important for international understanding:
Yard:
- 0.9144 meters (about 91 cm)
- Slightly shorter than a meter
- Used primarily in US, UK, Canada
- Based on foot (3 feet = 1 yard)
Meter:
- 1.09361 yards (about 9% longer)
- Slightly longer than a yard
- Global SI standard
- Based on metric system (100 cm = 1 meter)
Visual comparison:
- A meter stick is about 3.37 inches longer than a yardstick
- 100 yards = 91.44 meters (football field)
- 100 meters = 109.36 yards (Olympic track straightaway)
Mental approximation: For quick estimates, consider 1 yard ≈ 1 meter (about 9% difference is often negligible for casual use).
and Standards
Geometric Definition
The parsec is defined through trigonometric parallax:
1 parsec = the distance at which 1 astronomical unit (AU) subtends an angle of 1 arcsecond (1″)
Mathematically:
- 1 parsec = 1 AU / tan(1″)
- Since 1″ = 1/3600 degree = π/648,000 radians ≈ 4.8481 × 10⁻⁶ radians
- For small angles: tan(θ) ≈ θ (in radians)
- 1 parsec ≈ 1 AU / 4.8481 × 10⁻⁶ ≈ 206,265 AU
Exact IAU Value
The International Astronomical Union (IAU) defines the parsec exactly as:
1 parsec = 648,000/π AU ≈ 206,264.806247 AU
Using the IAU-defined astronomical unit (1 AU = 149,597,870,700 meters exactly as of 2012):
1 parsec = 30,856,775,814,913,673 meters (exactly)
Or approximately:
- 3.0857 × 10¹⁶ meters
- 30.857 trillion kilometers
- 19.174 trillion miles
Relationship to Light-Year
The light-year (distance light travels in one Julian year) relates to the parsec:
1 parsec ≈ 3.26156 light-years
More precisely: 1 pc = 3.261563777 ly (using Julian year of 365.25 days)
Standard Multiples
Kiloparsec (kpc): 1 kpc = 1,000 pc ≈ 3,262 ly
- Used for distances within galaxies
- Milky Way diameter: ~30 kpc
Megaparsec (Mpc): 1 Mpc = 1,000,000 pc ≈ 3.26 million ly
- Used for intergalactic distances
- Andromeda Galaxy: ~0.77 Mpc
Gigaparsec (Gpc): 1 Gpc = 1,000,000,000 pc ≈ 3.26 billion ly
- Used for cosmological distances
- Observable universe radius: ~14 Gpc
Note: The Yard is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Parsec belongs to the imperial/US customary system.
History of the Yard and Parsec
The origin of the yard is uncertain, with historical links possibly related to the length of a stride or the distance from the nose to the fingertip of an outstretched arm (associated with King Henry I of England, though likely apocryphal). It became a standard unit in England for measuring cloth and land, and was later precisely defined relative to the meter.
Early Origins (Pre-1000s)
Ancient roots:
The yard likely evolved from multiple ancient measurement systems:
Saxon "gerd" or "gyrd":
- Old English word meaning "stick," "rod," or "measure"
- Wooden measuring rods used by Anglo-Saxon merchants
- Roughly similar to modern yard but not standardized
Double cubit theory:
- Ancient cubit = elbow to fingertip (~18 inches)
- "Double cubit" = 36 inches = 1 yard
- Used by Romans, Egyptians, Babylonians
Body measurement origins:
- Stride length: Average adult pace (~1 yard)
- Arm span: Nose to fingertip of outstretched arm (apocryphal King Henry I story)
- These varied by individual, creating measurement inconsistency
Medieval Standardization (1100s-1500s)
When the yard became official:
1101: King Henry I "body measurement" legend:
- Popular story: Henry I decreed yard = distance from royal nose to extended thumb
- Likely apocryphal but reflects need for standardization
- Real achievement: Establishing royal standards to replace local variations
1266: Statute of Westminster under Henry III:
- First legal definition of the yard in English law
- Established: 1 yard = 3 feet (official relationship)
- Created iron "yard standards" kept at Westminster Palace
- Cloth merchants required to use standardized yards
1305: Edward I measurement reforms:
- Continued standardization efforts
- "Ell" (45 inches) used for some cloth, but yard became dominant
- Penalties for merchants using incorrect measures
1400s-1500s: Physical yard standards:
- Bronze and brass "yard bars" created as references
- Kept at London's Guildhall and markets
- Regional variations persisted despite standards
Tudor Era Refinement (1500s)
More precise definitions:
1588: Elizabethan Yard Standard:
- Queen Elizabeth I commissioned official "Imperial Standard Yard"
- Made of bronze with precise markings
- Stored at Westminster Palace (lost in 1834 fire)
- Used to verify merchant yardsticks
Textile trade importance:
- England's wool and cloth trade drove standardization
- Fabric sold "by the yard" required consistent measurement
- Export trade demanded international recognition
British Imperial Standardization (1800s)
Scientific precision era:
1824: Weights and Measures Act:
- Standardized imperial units across British Empire
- Yard officially defined in relation to physical prototype
- "Imperial Standard Yard" bar created
1834: Westminster Fire disaster:
- Fire destroyed Houses of Parliament
- Lost original yard standards, including Elizabethan bar
- Created measurement crisis requiring new standards
1855: New Imperial Standard Yard:
- Parliament commissioned replacement yard standard
- Defined as 36/39.370113 meters (based on contemporary meter definition)
- Bronze bar kept at constant temperature (62°F)
- Multiple copies distributed across British Empire
American Divergence (1800s-1950s)
US develops separate standard:
1790s-1830s: Early US measurements:
- United States inherited British yard from colonial era
- No official US standard until 1830s
- State and local variations common
1832: US Office of Weights and Measures:
- Created to standardize American measurements
- Obtained copies of British yard standards
- But slight differences existed between US and UK prototypes
1866: US Metric Act:
- Congress authorized metric system use
- Defined meter-to-yard relationship: 1 meter = 39.37 inches
- Still preserved traditional yard for common use
1893: Mendenhall Order:
- US officially defined yard in terms of meter
- 1 yard = 3,600/3,937 meters = 0.914401829 meters
- Slightly different from British yard (0.9144 m)
- Created UK-US measurement discrepancy
International Unification (1959)
Finally, one global yard:
July 1, 1959: International Yard and Pound Agreement:
- Signed by US, UK, Canada, Australia, New Zealand, South Africa
- Defined: 1 yard = exactly 0.9144 meters
- 1 inch = exactly 25.4 millimeters (derived)
- Unified measurements across English-speaking world
Why this mattered:
- Eliminated UK-US discrepancy (0.914401829 vs 0.9144 m)
- Simplified international trade and engineering
- Difference was tiny (2 parts per million) but critical for precision work
Survey yard exception:
- US land surveys continued using old definition until 2023
- "US Survey Yard" = 0.91440183 meters (pre-1959 standard)
- Created confusion in mapping/GIS
- January 1, 2023: US officially retired survey yard, adopted international yard
Modern Era (1960s-Present)
Metric pressure and yard persistence:
1960s-1970s: Global metrication:
- Most British Commonwealth nations adopted metric system
- Australia (1970s), Canada (1970s), UK (partially 1960s-80s)
- Yard usage declined in favor of meters
United States resistance:
- Rejected metric conversion despite 1975 Metric Conversion Act
- Yard remains standard for fabric, sports, construction
- Coexists with metric in science, medicine, military
Current status:
- Primary use: United States (everyday measurement)
- Limited use: UK (road distances in miles/yards, sports fields)
- Legacy use: Canada (construction, real estate alongside meters)
- Declining: Elsewhere, replaced by meters
and Evolution
Pre-Parsec Era: The Parallax Quest (1600s-1830s)
The concept of stellar parallax dates to ancient Greek astronomy, but detecting it required centuries of technological advancement.
Galileo Galilei (1610) suggested that if Earth orbits the Sun, nearby stars should show annual parallax shifts against distant background stars. No parallax was detected, leading geocentrists to argue Earth must be stationary.
James Bradley (1728) discovered stellar aberration (apparent star position shifts due to Earth's orbital motion combined with finite light speed), confirming Earth's motion but still failing to detect parallax—stars were simply too distant.
Friedrich Wilhelm Bessel achieved the first successful parallax measurement in 1838 for 61 Cygni, determining a distance of about 10.3 light-years (3.16 parsecs, though the term didn't exist yet). This triumph came using a heliometer—a split-lens telescope enabling precise angular measurements.
Thomas Henderson measured Alpha Centauri's parallax (1832-1833, published 1839), and Friedrich Struve measured Vega's (1837), establishing parallax as the fundamental distance measurement method.
Coining the Term (1913)
Herbert Hall Turner (1861-1930), British astronomer and director of Oxford University Observatory, coined "parsec" in 1913. Before this, astronomers expressed stellar distances awkwardly:
- In astronomical units (requiring numbers in the hundreds of thousands)
- In light-years (popular but not directly tied to measurement method)
- In "parallax seconds" (inverse of parallax angle, but confusing terminology)
Turner recognized that astronomers naturally thought in terms of parallax angles. For a star with parallax angle p (in arcseconds), the distance d is simply:
d (in parsecs) = 1 / p (in arcseconds)
This elegant relationship made the parsec immediately practical. A star with 0.5″ parallax is 2 parsecs away; 0.1″ parallax means 10 parsecs; 0.01″ parallax means 100 parsecs.
IAU Adoption (1922-1938)
The 1922 IAU General Assembly in Rome endorsed the parsec as the standard unit for stellar distances, though adoption wasn't immediate or universal.
The 1938 IAU General Assembly in Stockholm formally standardized the parsec definition based on the astronomical unit and arcsecond, solidifying its status.
By the 1950s, the parsec dominated professional astronomy literature, though popular science continued preferring light-years for general audiences.
Space Age Precision (1960s-Present)
Hipparcos satellite (1989-1993): European Space Agency mission measured parallaxes for 118,000 stars with milliarcsecond precision, extending reliable parsec-based distances to hundreds of parsecs.
Gaia mission (2013-present): ESA's Gaia spacecraft has revolutionized astrometry, measuring parallaxes for 1.8 billion stars with microarcsecond precision. This extends direct parsec measurements to 10,000+ parsecs (10+ kiloparsecs), mapping our galaxy's structure in unprecedented detail.
2012 IAU redefinition: The IAU redefined the astronomical unit as exactly 149,597,870,700 meters (no longer based on Earth's actual orbit, which varies slightly). This made the parsec exactly 648,000/π AU, providing a stable definition independent of Earth's orbital variations.
Common Uses and Applications: yards vs parsecs
Explore the typical applications for both Yard (imperial/US) and Parsec (imperial/US) to understand their common contexts.
Common Uses for yards
Textiles and Fabric Industry
Measuring fabric length (often sold by the yard).
Why yards persist in fabric:
- Historical: English wool trade established "yard goods" standard
- Bolt widths designed around yard fractions
- Cutting tables marked in yards
- Pattern instructions written in yards
Standard practices:
- Minimum purchase: Often 0.25 yard (9 inches)
- Common increments: Sold in 1/8 yard (4.5 in), 1/4 yard, 1/2 yard, 1 yard
- Remnants: Odd lengths sold at discount
- Wholesale: Fabric bolts typically 10-20 yards
International comparison:
- Metric countries: Fabric sold by meter
- Pattern conversion: 1 yard ≈ 0.91 meters (patterns provide both)
Sports Field Dimensions
Dimensions of sports fields (e.g., American football, soccer pitch lengths can be expressed in yards).
American football:
- Standard 100-yard × 53⅓-yard field
- Universal across high school, college, NFL
- Goal posts width: 18.5 feet (6.17 yards)
Soccer/association football:
- US youth fields: Often expressed in yards (e.g., "60 yards × 40 yards")
- International: Meters (100-110m × 64-75m)
- Conversion needed: FIFA-sized field ~120 yards × 80 yards
Cricket:
- Pitch length: 22 yards (20.12 meters) between wickets
- Boundary: Varies, typically 65-90 yards radius
Lacrosse:
- Men's field: 110 yards × 60 yards
- Women's field: Varies, typically 120 yards × 70 yards
Landscaping and Gardening
Landscaping and gardening measurements (e.g., yards of mulch).
Bulk materials:
- Mulch: "$35 per cubic yard delivered"
- Topsoil: Cubic yards for garden beds
- Gravel/crushed stone: Driveway base in cubic yards
- Compost: Bulk delivery by cubic yard
Coverage calculations:
- 1 cubic yard of mulch: Covers ~100 sq ft at 3-inch depth
- 1 cubic yard of topsoil: Covers ~100 sq ft at 3-inch depth
- Landscape fabric: Sold by linear yard (typically 3-4 feet wide)
Garden planning:
- Raised bed dimensions: "4 yards long × 1 yard wide"
- Irrigation: Pipe and hose measured in yards
- Hedge spacing: "Plant every 1 yard for privacy"
Short to Medium Distance Measurement
Shorter road distances or property dimensions in the US and UK.
Road signage (UK):
- Warning signs: "200 yards ahead"
- Distance markers: "Services 300 yards"
- US: Mostly uses feet for short road distances
Property and real estate:
- Lot frontage: "100 yards of waterfront"
- Setbacks: Building code requirements in yards
- Fencing: "Install 200 yards of fencing"
Navigation:
- GPS directions: "In 50 yards, turn right" (some devices)
- Marine navigation: Prefer nautical miles, but yards for close quarters
- Aviation: Use feet for altitude, nautical miles for distance
Military and Defense
Historically significant:
Rifle ranges:
- 100-yard zero: Common rifle sight-in distance
- 200/300/500 yards: Marksmanship qualification distances
- Long-range shooting: Expressed in yards (e.g., "1,000-yard shot")
Military exercises:
- Formations: Squad spacing in yards
- Radio calls: "Enemy position 300 yards north"
- Artillery: Modern systems use meters, but yards persist in US training
When to Use parsecs
Stellar Astronomy and Parallax Measurements
The parsec's primary use is measuring stellar distances via trigonometric parallax:
Parallax formula: d (parsecs) = 1 / p (arcseconds)
Ground-based observatories: Measure parallaxes to ~0.01″ accuracy, reliable to ~100 pc
Hipparcos satellite: Measured parallaxes to ~0.001″ (1 milliarcsecond), reliable to ~1,000 pc (1 kpc)
Gaia spacecraft: Measures parallaxes to ~0.00001″ (10 microarcseconds) for bright stars, reliable to ~10 kpc for many stars
Applications:
- Calibrating the cosmic distance ladder (using Cepheid variables, RR Lyrae stars)
- Determining absolute magnitudes of stars
- Studying stellar populations and galactic structure
- Measuring proper motions and space velocities
Galactic Structure and Dynamics
Kiloparsecs (kpc) describe structures within galaxies:
Milky Way structure:
- Galactic center (Sagittarius A*): 8.2 kpc from Sun
- Galactic disk radius: ~15 kpc
- Central bulge: ~1.5 kpc radius
- Spiral arms: trace patterns 10-15 kpc in radius
- Dark matter halo: extends to ~60 kpc
Rotation curves: Plot orbital velocity vs. distance (in kpc) from galactic center, revealing dark matter
Star formation regions: Giant molecular clouds span 10-100 pc
Globular clusters: Orbit 10-60 kpc from galactic center
Extragalactic Astronomy
Megaparsecs (Mpc) measure distances between galaxies:
Galaxy surveys: Map millions of galaxies to distances of 1,000+ Mpc, revealing large-scale structure (walls, filaments, voids)
Tully-Fisher relation: Links galaxy rotation speed to luminosity, enabling distance estimates in Mpc
Type Ia supernovae: Standard candles for measuring distances to 1,000+ Mpc
Galaxy clusters: Typical separation between major clusters ~10-50 Mpc
Superclusters: Structures spanning 100-200 Mpc (like Laniakea Supercluster containing Milky Way)
Cosmology and Universe Expansion
Megaparsecs and gigaparsecs describe cosmological distances:
Hubble constant (H₀): Measured in km/s per Mpc—describes universe expansion rate
- Current value: H₀ ≈ 67-73 (km/s)/Mpc (tension between measurement methods)
- Interpretation: Galaxy 1 Mpc away recedes at ~70 km/s; 100 Mpc away recedes at ~7,000 km/s
Hubble's Law: v = H₀ × d (where d is in Mpc, v is recession velocity)
Comoving distance: Cosmological distance accounting for universe expansion, measured in Mpc or Gpc
Redshift surveys: Map galaxy distribution to 1,000+ Mpc (z ~ 0.1-0.3 redshift)
Baryon acoustic oscillations: ~150 Mpc characteristic scale in galaxy distribution, used as "standard ruler"
Astrophysical Research Papers
Parsecs are the default distance unit in professional astronomy journals:
Observational papers: Report star/galaxy distances in pc, kpc, or Mpc
Theoretical models: Express scale lengths in parsecs (e.g., "disk scale length of 3 kpc")
Computer simulations: Use parsec-based units (or comoving kpc/Mpc for cosmological sims)
Standard convention: Professional astronomers think and calculate in parsecs, converting to light-years only for public communication
Additional Unit Information
About Yard (yd)
How many feet are in a yard?
There are exactly 3 feet (ft) in 1 yard (yd). This is the fundamental relationship defining the yard. For example: 5 yards = 15 feet, 10 yards = 30 feet, and 100 yards (a football field) = 300 feet.
How many inches are in a yard?
There are exactly 36 inches (in) in 1 yard (yd). Since 1 yard = 3 feet and 1 foot = 12 inches, multiply: 3 × 12 = 36 inches. This is useful for fabric cutting and precise measurements.
Is a yard longer or shorter than a meter?
A yard (0.9144 m) is slightly shorter than a meter (1 m) by approximately 9.4% or about 3.37 inches. Think of it this way: 100 yards = 91.44 meters, or conversely, 100 meters = 109.36 yards. A yardstick is visibly shorter than a meter stick when placed side by side.
How many yards are in a mile?
There are 1,760 yards in 1 mile (statute mile). This means a half-mile = 880 yards, and a quarter-mile = 440 yards. For reference, a standard running track is 440 yards (or 400 meters in modern tracks), representing one-quarter of a mile.
Why is fabric sold by the yard?
Fabric is sold by the yard in the US due to historical English textile trade practices from the medieval period when the yard became the standard cloth measurement. Fabric bolts are manufactured in yard-friendly widths (typically 36, 45, 54, or 60 inches), and cutting tables are marked in yards. Sewing patterns specify fabric requirements in yards, making it the standard for the American crafting and fashion industries. Internationally, fabric is sold by the meter in metric countries.
How do I measure a yard without a ruler?
Body-based approximations:
- Adult stride: Average adult walking pace is approximately 1 yard (may vary by height)
- Arm span approximation: Nose to fingertip of outstretched arm is roughly 1 yard (the apocryphal King Henry I method)
- 3 shoe lengths: Average adult shoe is about 12 inches, so 3 shoes ≈ 36 inches = 1 yard
Household objects:
- Door height: Standard door is 80 inches (2.22 yards)
- Floor tiles: 12-inch square tiles → 3 tiles in a row = 1 yard
- Credit card: 3.37 inches wide → 10.7 cards = 1 yard (not practical, but mathematically interesting)
Best method: Mark a stick or string at 36 inches using a ruler once, then use it as a reusable yard measure.
What is a "square yard"?
A square yard (yd²) is a unit of area equal to a square measuring 1 yard on each side. Since 1 yard = 3 feet, 1 square yard = 9 square feet (3 ft × 3 ft). This is used for measuring carpet, flooring, landscaping coverage, and room areas. For example, a 10 ft × 12 ft room = 120 square feet = 13.33 square yards.
What is a "cubic yard"?
A cubic yard (yd³) is a unit of volume equal to a cube measuring 1 yard on each side. Since 1 yard = 3 feet, 1 cubic yard = 27 cubic feet (3 ft × 3 ft × 3 ft). This is the standard unit for ordering concrete, mulch, soil, gravel, and other bulk materials in the US. For example, a concrete truck typically carries 10 cubic yards, and 1 cubic yard of mulch covers approximately 100 square feet at 3-inch depth.
Why do American football fields use yards?
American football fields use yards because the sport originated in the United States in the late 1800s when imperial units were the standard measurement system. The 100-yard field length provides convenient divisions: 4 quarters of 25 yards each, 10-yard first-down increments, and easy mental arithmetic for players and fans. Changing to meters (100m = 109.36 yards) would create awkward field dimensions and disrupt the sport's traditional structure. The yard remains deeply embedded in football culture and rule books.
Are yards still used in the UK?
Yes, but usage is mixed and declining. The UK officially adopted the metric system in the 1960s-1990s, but yards persist in certain contexts:
- Road signs: Distances under 1 mile often shown in yards ("Services 200 yards")
- Sports: Cricket (22-yard pitch), some golf courses
- Informal speech: Older generations may say "a few yards away"
- Fabric shops: Some still sell by the yard, but meters increasingly common
Not used: Most construction, engineering, education now use meters. Younger generations primarily think in metric.
Can I use yards and meters interchangeably?
For rough estimates: Yes (about 10% difference often negligible) For precision work: No (9.4% difference accumulates)
When interchangeable works:
- Casual conversation ("it's about 50 yards/meters away")
- Rough project planning
- Approximate sports distances
When you need exact conversion:
- Fabric orders (5 yards ≠ 5 meters - you'd be short 43 cm)
- Construction blueprints
- Athletic competition (100-yard dash ≠ 100-meter dash)
- International trade
Best practice: Convert explicitly using 1 yard = 0.9144 meters for any situation requiring accuracy.
About Parsec (pc)
What does "parsec" stand for?
Parsec is a portmanteau of "parallax of one arcsecond."
It represents the distance at which Earth's orbital radius (1 AU) subtends an angle of exactly one arcsecond (1/3600 of a degree). British astronomer Herbert Hall Turner coined the term in 1913 to provide a convenient unit directly tied to the parallax measurement method.
How is a parsec measured?
Parsecs are measured using trigonometric parallax:
- Observe a nearby star from Earth when Earth is on one side of its orbit
- Observe the same star six months later when Earth is on the opposite side
- Measure the apparent shift in the star's position against distant background stars
- Half this shift is the parallax angle p (in arcseconds)
- Calculate distance: d = 1/p parsecs
Modern method: Space telescopes like Gaia measure parallax angles with microarcsecond precision, enabling distance measurements to thousands of parsecs.
Is a parsec bigger than a light-year?
Yes, one parsec is significantly larger:
1 parsec ≈ 3.26 light-years
More precisely: 1 pc = 3.261563777 ly
Example: Proxima Centauri at 1.3 parsecs equals 4.24 light-years away.
Why the difference matters: Confusing parsecs with light-years introduces 3× error in distances.
Why do astronomers prefer parsecs over light-years?
Astronomers prefer parsecs for several reasons:
1. Direct observational connection: Parallax angle p (arcseconds) directly gives distance d = 1/p (parsecs). No complicated conversion needed.
2. Professional standard: IAU endorsed parsecs in 1922; they're now universal in research papers and textbooks.
3. Convenient multiples: Kiloparsecs (kpc) for galactic distances, megaparsecs (Mpc) for cosmological distances provide natural scales.
4. Hubble constant units: Universe expansion rate naturally expressed in (km/s)/Mpc.
5. Definition stability: Light-year depends on year length definition (tropical, Julian, sidereal); parsec defined purely by geometry.
Light-years remain popular in public communication because "year" is familiar, while "parallax arcsecond" requires technical knowledge.
How many astronomical units are in a parsec?
1 parsec = 206,265 astronomical units (AU) (approximately)
More precisely: 1 pc = 206,264.806247 AU
This number arises from: 1 pc = 1 AU / tan(1″), and since 1″ = π/648,000 radians:
- 1 pc = 1 AU / (π/648,000) = 648,000/π AU ≈ 206,265 AU
Context: Since 1 AU ≈ 150 million km (Earth-Sun distance), 1 parsec ≈ 31 trillion km.
What is a kiloparsec and megaparsec?
Kiloparsec (kpc): 1 kpc = 1,000 parsecs ≈ 3,262 light-years
- Used for: Galactic-scale distances
- Examples: Sun to Milky Way center (8 kpc), galaxy diameters (10-50 kpc)
Megaparsec (Mpc): 1 Mpc = 1,000,000 parsecs ≈ 3.26 million light-years
- Used for: Intergalactic distances, cosmology
- Examples: Andromeda Galaxy (0.77 Mpc), Virgo Cluster (16.5 Mpc), Hubble constant measured in (km/s)/Mpc
Gigaparsec (Gpc): 1 Gpc = 1,000,000,000 parsecs ≈ 3.26 billion light-years
- Used for: Large-scale cosmological structures
- Example: Observable universe radius (~14 Gpc)
Is the parsec an SI unit?
No, the parsec is not an SI unit. The SI unit of length is the meter (m).
However, the parsec is:
- Recognized by the IAU (International Astronomical Union)
- Accepted for use with SI in astronomy contexts
- Defined exactly in terms of the AU (which is defined exactly in meters)
Why not SI?: The parsec arose naturally from astronomical practice and remains far more practical than expressing stellar distances in meters (which would require numbers like 10¹⁶ to 10²³).
Analogy: Like the electronvolt (eV) in particle physics, the parsec is a specialized unit indispensable to its field despite not being SI.
How far can parallax measure distances?
Ground-based telescopes: ~0.01 arcsecond precision → reliable to ~100 parsecs
Hubble Space Telescope: ~0.001 arcsecond (1 milliarcsecond) → reliable to ~1,000 parsecs (1 kpc)
Hipparcos satellite (1989-1993): ~0.001 arcsecond → 118,000 stars measured to 100-1,000 pc
Gaia spacecraft (2013-present): ~0.00001 arcsecond (10 microarcseconds) for bright stars → reliable to ~10,000 parsecs (10 kpc)
- Measured 1.8 billion stars
- Revolutionary precision enables mapping entire Milky Way disk
Fundamental limit: Stars beyond 10-20 kpc have unmeasurably small parallaxes with current technology. For greater distances, astronomers use indirect methods (Cepheids, Type Ia supernovae, redshift).
Did Han Solo make the Kessel Run in "less than 12 parsecs"?
Famous Star Wars quote: "She made the Kessel Run in less than twelve parsecs."
The issue: Parsec measures distance, not time. Saying "less than 12 parsecs" for a speed achievement is like saying "I drove to work in less than 5 miles."
Fan explanations (retroactive justifications):
- The Kessel Run involves navigating near black holes; a shorter distance means a more dangerous, direct route
- Skilled pilots can shave distance by flying closer to gravitational hazards
- This reinterprets "12 parsecs" as boasting about route optimization, not speed
Real answer: George Lucas likely confused parsecs with a time unit when writing the script. The line became famous enough that later writers invented explanations making it technically correct.
Takeaway: In real astronomy, parsecs always measure distance, never time.
How do parsecs relate to the Hubble constant?
The Hubble constant (H₀) describes universe expansion and is typically expressed as:
H₀ ≈ 70 (km/s)/Mpc
Interpretation: For every megaparsec of distance, recession velocity increases by ~70 km/s.
Examples using Hubble's Law (v = H₀ × d):
- Galaxy 1 Mpc away: recedes at ~70 km/s
- Galaxy 10 Mpc away: recedes at ~700 km/s
- Galaxy 100 Mpc away: recedes at ~7,000 km/s
- Galaxy 1,000 Mpc away: recedes at ~70,000 km/s
Hubble length: c/H₀ ≈ 4,400 Mpc (14.4 billion ly) - characteristic distance scale of observable universe
Why Mpc?: Using megaparsecs keeps Hubble constant values convenient (70 rather than 0.000000000070 if using parsecs, or 2.3 × 10⁻¹⁸ if using SI meters).
What's the farthest distance ever measured in parsecs?
Observable universe radius: ~14,000 Mpc = 14 Gpc (46 billion light-years comoving distance)
Most distant galaxy observed (as of 2023): JADES-GS-z13-0 at redshift z ≈ 13.2
- Comoving distance: ~4,200 Mpc (13.7 billion light-years light-travel distance)
- Due to universe expansion, it's now ~10,000 Mpc (32 billion light-years) away
Cosmic microwave background: Emitted 380,000 years after Big Bang
- Comoving distance to CMB surface: ~14,000 Mpc (46 billion light-years)
Beyond measurement: The observable universe has a finite size (~14 Gpc radius) due to finite age and light speed. Objects beyond this "cosmological horizon" are unobservable because their light hasn't reached us yet.
Conversion Table: Yard to Parsec
| Yard (yd) | Parsec (pc) |
|---|---|
| 0.5 | 0 |
| 1 | 0 |
| 1.5 | 0 |
| 2 | 0 |
| 5 | 0 |
| 10 | 0 |
| 25 | 0 |
| 50 | 0 |
| 100 | 0 |
| 250 | 0 |
| 500 | 0 |
| 1,000 | 0 |
People Also Ask
How do I convert Yard to Parsec?
To convert Yard to Parsec, enter the value in Yard in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our length converter page to convert between other units in this category.
Learn more →What is the conversion factor from Yard to Parsec?
The conversion factor depends on the specific relationship between Yard and Parsec. 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 Parsec back to Yard?
Yes! You can easily convert Parsec back to Yard by using the swap button (⇌) in the calculator above, or by visiting our Parsec to Yard converter page. You can also explore other length conversions on our category page.
Learn more →What are common uses for Yard and Parsec?
Yard and Parsec are both standard units used in length measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our length converter for more conversion options.
For more length conversion questions, visit our FAQ page or explore our conversion guides.
Helpful Conversion Guides
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📚 How to Convert Units
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🔢 Conversion Formulas
Essential formulas for length and other conversions.
⚖️ Metric vs Imperial
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⚠️ Common Mistakes
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All Length Conversions
Other Length Units and Conversions
Explore other length units and their conversion options:
- Meter (m) • Yard to Meter
- Kilometer (km) • Yard to Kilometer
- Hectometer (hm) • Yard to Hectometer
- Decimeter (dm) • Yard to Decimeter
- Centimeter (cm) • Yard to Centimeter
- Millimeter (mm) • Yard to Millimeter
- Inch (in) • Yard to Inch
- Foot (ft) • Yard to Foot
- Mile (mi) • Yard to Mile
- Nautical Mile (NM) • Yard to Nautical Mile
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 — Official US standards for length measurements
Bureau International des Poids et Mesures — International System of Units official documentation
Last verified: December 3, 2025