Nepedia
Back to Discover
Advanced Reader
🔢

Furlong

math Maturity 5-7 Next article →

A furlong is a unit of distance used in imperial and United States customary systems. It represents exactly one-eighth of a mile. You can also define it through several other measurements. One furlong equals 660 feet or 220 yards. It is also equivalent to 40 rods, also known as perches, or 10 chains. In the metric system, a furlong is approximately 201 metres. Specifically, using the international yard of 0.9144 metres, a furlong is exactly 201.168 metres.

036175 5 furlong
036175 5 furlong

This measurement is highly useful because five furlongs equal almost exactly one kilometre.

The mechanism of the furlong is tied to how it relates to other land measurements. It acts as a building block for larger areas like the acre. An acre is defined as an area that is one furlong long and one chain wide. This creates a shape that is 40 rods by 4 rods, totaling 160 square rods. Historically, a square furlong contains exactly 10 acres. This mathematical relationship allowed early surveyors to calculate large fields using simple ratios. The system relies on these consistent proportions to maintain accuracy across different scales of land.

There are several distinct ways the furlong is applied today. In most English-speaking countries, it is a standard measurement for horse racing lengths. In the United Kingdom, it is also used to express distances along canals navigated by narrowboats. Some cities use the furlong to define their urban layouts. For example, Chicago uses a system where eight blocks make up one mile. This means a typical city block is approximately one furlong in length. Other cities, like Salt Lake City and Phoenix, use square furlongs for their downtown blocks.

The history of the furlong begins with the agricultural needs of the Anglo-Saxons. The name comes from the Old English words for "furrow" and "long." A furrow is the long line made in a field by a plough. Originally, a furlong was the distance a team of oxen could plough before needing a rest. Turning a heavy team of oxen was a difficult task for farmers. To avoid frequent turns, they created long furrows. This practice established the furlong as a standard length of 40 rods or 10 chains.

Measurement standards changed significantly in the late 13th century in England. Before this, the Saxons used the North German foot, which was 10 percent longer than the modern international foot. When England adopted a shorter foot, the rods and furlongs themselves stayed the same. Only the number of feet and yards within them changed. A furlong moved from 600 old feet to 660 new feet. Similarly, an acre changed from 36,000 old square feet to 43,560 new square feet. This transition ensured that existing property boundaries remained valid even as the base units evolved.

Significant variations in the furlong have existed due to different national standards. In the United States, some states used the U.S. survey foot for surveying. This created a tiny difference of about two parts per million compared to the international definition. This variation was too small to cause practical problems for most people. However, the U.S. National Geodetic Survey and NIST decided to retire the survey foot. By the end of 2022, the United States moved to the international definition. Now, a furlong in the U.S. is exactly 201.168 metres, just like in Canada and the UK.

The furlong connects to many different fields, from history to modern urban planning. In Ontario, Canada, many major roads follow a ten-furlong grid. Because of this, these roads are often spaced almost exactly two kilometres apart. In Myanmar, highway signs still use miles and furlongs to show distances.

Milepost 358-6 on Yangon-Mandalay Expressway
Milepost 358-6 on Yangon-Mandalay Expressway

Even in specialized academic settings, the furlong appears in humorous unit systems. It remains a lasting legacy of how ancient farming practices shaped the way we measure the world today.

643 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (2)
File:Milepost 358-6 on Yangon-Mandalay Expressway.JPG
Milepost 358-6 on Yangon-Mandalay Expressway.JPG
File:036175 5 furlong.jpg
036175 5 furlong.jpg
More to explore

🔬 Go deeper

More advanced topics to explore

🪜 Step back

Simpler topics to build understanding

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.