Furlong to Millimeter Converter

The Eighth of a Mile

The furlong is defined as exactly 1/8 of a statute mile.

Precise equivalents:

• 220 yards (1/8 × 1,760 yards)
• 660 feet (220 yards × 3 feet/yard)
• 40 rods (traditional surveying unit; 1 rod = 16.5 feet)
• 10 chains (1 chain = 66 feet = 4 rods)
• 201.168 meters (exactly, using 1 yard = 0.9144 m)

Old English Etymology

"Furlang" = "furrow-long"

• Furh (Old English) = furrow (a trench cut by a plow)
• Lang (Old English) = long

Agricultural origin: In medieval open-field farming, peasants plowed long, narrow strips. The furlong represented the standard length of these strips—the distance a team of oxen could pull a heavy plow before needing to rest and turn around.

Why this specific distance?

• Oxen stamina: Approximately 220 yards before fatigue
• Practical turn-around: Long enough to be efficient, short enough to manage
• Acre relationship: 1 furlong × 1 chain (66 ft) = 1 acre (historical definition)

The Chain-Furlong-Mile System

Edmund Gunter's surveyor's chain (1620):

• 1 chain = 66 feet = 4 rods = 100 links
• 10 chains = 1 furlong
• 80 chains = 1 mile

Why 66 feet? Gunter designed the chain so that:

• 10 square chains = 1 acre (exactly)
• Easy conversion between area and distance
• Practical length for field surveying (two surveyors could carry it)

This system dominated English-speaking land surveys for 300+ years.

Anglo-Saxon Origins (5th-11th Centuries)

Open-field strip farming: Medieval English villages practiced communal agriculture, with fields divided into long, narrow strips assigned to different families.

Strip dimensions:

• Length: 1 furlong (~220 yards)
• Width: 1 chain (~22 yards, later standardized to 1 chain = 66 feet / 4 rods)
• Area: Approximately 1 acre

Plowing practice: Farmers plowed the length of the strip (1 furlong), then turned the ox team at the headland (the unplowed area at each end). The furlong emerged as the natural unit for this plowing distance.

Norman and Plantagenet Standardization (11th-14th Centuries)

Domesday Book (1086): William the Conqueror's land survey used furlongs and acres to catalog English landholdings, cementing these units in law.

Statute of 1305 (Edward I): Formalized the furlong as:

• 40 rods (1 rod = 16.5 feet = 5.5 yards)
• 1/8 mile
• Standard for all land measurement in England

Acre definition: Legally defined as 1 furlong × 4 rods (1 furlong × 66 feet), creating the enduring acre-furlong relationship.

Edmund Gunter and the Surveyor's Chain (1620)

Revolutionary tool: English mathematician Edmund Gunter invented the surveyor's chain, a 66-foot measuring chain with 100 links.

Advantages:

• Durability: Metal chain resisted wear better than ropes
• Accuracy: Standardized links prevented stretching errors
• Calculation ease: 100 links made decimal-like subdivision simple
• Furlong integration: 10 chains = 1 furlong (exact)

Global spread: Gunter's chain became the standard surveying tool throughout the British Empire, spreading the furlong to:

• North America (colonial land surveys)
• Australia (1788 onwards)
• India (British Raj)
• Africa (colonial territories)

Horse Racing Adoption (18th Century)

The Jockey Club (founded 1750): British horse racing's governing body standardized race distances in furlongs and miles.

Common race distances established:

• 5 furlongs: Sprint races
• 1 mile (8 furlongs): Classic middle distance
• 1.5 miles (12 furlongs): St. Leger Stakes (established 1776)
• 2.5 miles (20 furlongs): Royal Ascot Gold Cup

Why furlongs?

• Traditional British measurement
• Convenient divisions of the mile
• Allowed precise race distance specifications
• Established in racecourse infrastructure (distance poles)

American Horse Racing (19th Century)

Kentucky Derby (1875): Established at 1.5 miles (12 furlongs), later shortened to 1.25 miles (10 furlongs) in 1896. The furlong became America's standard racing measurement.

Belmont Stakes (1867): Originally 1.625 miles, standardized to 1.5 miles (12 furlongs)—the "Test of the Champion."

Preakness Stakes (1873): Run at 9.5 furlongs (1.1875 miles).

All three Triple Crown races use furlong-based distances.

Metrication and Decline (20th Century)

UK Weights and Measures Act (1985): Officially transitioned Britain to metric system for most purposes. The furlong became obsolete for:

• Road distances (now kilometers)
• Land surveying (now meters)
• General measurement (meters standard)

Exception: Horse racing Racing authorities worldwide retained furlongs, grandfathered as a traditional sporting measure.

Modern Persistence (21st Century)

Countries still using furlongs in horse racing:

• United Kingdom: All thoroughbred racing
• Ireland: All thoroughbred racing
• United States: All thoroughbred and quarter horse racing
• Canada: Thoroughbred racing
• Australia: Some racing uses furlongs alongside meters
• Myanmar (Burma): Road signs and general distance measurement

Global standard: Despite metrication, international horse racing maintains furlong terminology for consistency with historical records and tradition.

1. Thoroughbred Horse Racing

Race distance specification: Nearly all English-language racing nations specify race lengths in furlongs.

Examples:

• "A 6-furlong sprint on turf"
• "The colt won at distances from 8 to 12 furlongs"
• "She specializes in 5-furlong races"

Racecourse markers: Distance poles along the track show remaining furlongs to the finish (e.g., "4F" pole = 4 furlongs to go).

2. Breeding and Training

Horse pedigrees: Thoroughbred bloodlines are analyzed by optimal racing distances measured in furlongs.

Example: "This stallion's progeny excel at 8-10 furlongs, inheriting his stamina."

Training distances: Trainers describe workout distances in furlongs: "We gave him a strong 6-furlong breeze this morning."

3. Myanmar (Burma)

Road distances: Myanmar road signs often show distances in furlongs and miles rather than kilometers.

Example: "Yangon 12 furlongs" (1.5 miles ahead)

Why? British colonial legacy; Myanmar has resisted full metrication.

4. Historical Documents

Land deeds: Property descriptions in English-speaking countries often reference furlongs:

"Beginning at the oak tree, thence north 3 furlongs, thence east 2 furlongs..."

Literary references: Classic literature mentions furlongs for travel distances.