Acres to Jō (tatami Mat) (ac to jō)

1 acre equals 2,448.348136 jō (tatami mat) (rounded).

1 acre = 2,448.348136 jō (tatami mat)

How to convert acres to jō (tatami mat)

To convert acres to jō (tatami mat), multiply the number of acres by 2,448.348136. The factor is rounded to 10 significant digits. To go the other way, multiply jō (tatami mat) by 0.0004084386471 (rounded).

jō (tatami mat) = acres × 2,448.348136

Example: 10 acres = 24,483.48136 jō (tatami mat).

Approximate value. Standards for the jō (tatami mat) varied by place and period, so this converter uses the most commonly cited value. Treat results as estimates, not exact figures.

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

Jō (tatami Mat) (jō)

JapaneseTraditional unit (still used in some regions)Approximate value

Half a tsubo, about 1.653 m², the area of one tatami mat. Mats vary by region from about 1.44 to 1.82 m², and Japanese real-estate rules set a minimum of 1.62 m² per jō in advertisements.

Jō is the counter for tatami, the woven rush floor mats of Japanese rooms, and the word tatami comes from a verb meaning to fold or pile, since early mats were thin enough to be stacked away. Tatami began as seating for the aristocracy in the Heian period and covered whole rooms in samurai and temple houses by the Muromachi era. They reached ordinary homes only in the late 17th century.

Because a mat was a standard building module, rooms are still described as six jō or eight jō. A mat is about twice as long as it is wide, and size varies by region. Kyoto mats measure about 191 by 95.5 cm, around 1.82 m2, Nagoya mats about 1.65 m2 and Tokyo mats about 1.55 m2. Apartment-block mats can be smaller, near 1.44 m2.

Wikipedia takes the Nagoya mat as the reference, which makes one jō half a tsubo, exactly 200/121 m2 or about 1.653 m2, and that is the figure used here. A separate figure of 1.62 m2 is the minimum area per mat that Japanese property advertising rules allow when a room is described by its mat count, so it is a legal floor rather than a typical mat.

1 jō (tatami mat) = 1.652892562 square meters (approximately).

Sources: Wikipedia: Japanese units of measurement; Wikipedia: Tatami; Real Estate Tokyo: Units used for real estate size in Japan

Related conversions

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