Acres to Tan (ac to tan)

1 acre equals 4.080580226 tan (rounded).

1 acre = 4.080580226 tan

How to convert acres to tan

To convert acres to tan, multiply the number of acres by 4.080580226. The factor is rounded to 10 significant digits. To go the other way, multiply tan by 0.2450631882 (rounded).

tan = acres × 4.080580226

Example: 10 acres = 40.80580226 tan.

About these units

Acre (ac)

US & ImperialCurrent unit

43,560 square feet or exactly 4,046.8564224 m², about 40% of a hectare. Originally the area a yoke of oxen could plow in a day.

Ploughland gave the acre its name: it traces to Old Norse akr, meaning cultivated land, and is related to German Acker and Latin ager. In medieval England it was a farming measure, the land one man with a team of eight oxen could plough in a day. The traditional strip was 40 perches long and 4 perches wide, which is 660 by 66 feet, or ten square chains. The shape was never the point, and the article on the unit stresses that any area of 43,560 square feet is an acre.

An acre is 43,560 square feet, 4,840 square yards or 1/640 of a square mile, close to 0.4 hectare. For Americans, it is roughly 88 by 55 yards, about 90 percent of a football field without the end zones. The Weights and Measures Act 1878 fixed it at 4,840 square yards in Britain, where trade use ended in 1995. The 1959 international acre is exactly 4,046.8564224 m²; the US survey acre, about 4,046.872 m², differed slightly, and US survey units were retired after 2022.

1 acre = 4,046.856422 square meters (approximately).

Sources: Wikipedia: Acre; NIST Guide to the SI, Appendix B.8: conversion factors

Tan (tan)

JapaneseTraditional unit (still used in some regions)

300 tsubo (about 991.74 m²), about a quarter of an acre. A traditional measure of farmland.

Rice paddies were counted in tan. One tan is 300 tsubo, or exactly 120,000/121 square metres, about 991.7, which is slightly less than a quarter of an acre. It equals ten se, and ten tan make a cho, so a farmer with several tan had a modest holding by the standards of the tax registers.

The unit belongs to the same system that valued land in koku of rice. Under the Tokugawa shogunate the kokudaka assessed a plot by its yield, and surveyed land was recorded in these agricultural areas. A common claim that one tan was the area needed to grow one koku is not confirmed by the sources consulted, so it should be taken as a rough tradition.

Japan signed the Metre Convention in 1885 and the 1891 weights and measures law gave the traditional units fixed metric equivalents. The Measurements Law of 1951 moved the country to metric units from 1959, and the tan survives mainly in rural land transactions and in talk of rice farming.

1 tan = 991.7355372 square meters (approximately).

Sources: Wikipedia: Japanese units of measurement; Wikipedia: Kokudaka; Wikipedia: Koku

Related conversions

See all area units.