Square Millimeters to Tsubo (mm² to tsubo)

1 square millimeter equals 3.025×10⁻⁷ tsubo exactly.

1 square millimeter = 3.025×10⁻⁷ tsubo

How to convert square millimeters to tsubo

To convert square millimeters to tsubo, multiply the number of square millimeters by 3.025×10⁻⁷. This factor is exact. To go the other way, multiply tsubo by 3,305,785.124 (rounded).

tsubo = square millimeters × 3.025×10⁻⁷

Example: 10 square millimeters = 0.000003025 tsubo.

About these units

Square Millimeter (mm²)

Metric (SI)Current unit

A square one millimeter on a side. Used for the cross-section of wires and small parts.

Gauss gets the credit for putting the millimeter at the base of a scientific measuring system. His 1832 proposal for absolute units used the millimeter, milligram and second, although the centimeter-based CGS system later won out among scientists. The square millimeter is a one-thousandth-by-one-thousandth square of a meter, so it takes a million of them to make a square meter, and it has no famous inventor of its own.

Electricians know it best. Wire and cable sizes are given as the cross-sectional area of the copper conductor, and the standard sizes listed for UK domestic wiring are 1, 1.5, 2.5, 4, 6 and 10 mm². Twin and earth cable of 2.5 mm² typically serves sockets on a 16 A radial or 32 A ring circuit, 1 mm² serves lighting on a 6 A breaker, and 4 mm² feeds a cooker or shower. Conductor size depends on current capacity and allowed voltage drop, not on voltage alone. One square inch is exactly 645.16 mm², so small parts in either system compare easily.

1 square millimeter = 0.000001 square meters (exactly).

Sources: Wikipedia: Electrical wiring in the United Kingdom; Wikipedia: Centimetre-gram-second system of units; Wikipedia: Square metre

Tsubo (tsubo)

JapaneseTraditional unit (still used in some regions)

Exactly 400/121 m² (3.3058 m²), one square ken: about two tatami mats. Still the usual unit for land and property prices in Japan.

Walk into a Japanese estate agent's window and the land is still priced per tsubo. The unit is the area of a square ken, which is six shaku on a side, so 36 square shaku. Once the shaku was fixed at 10/33 metre, the tsubo followed as exactly 400/121 square metres, about 3.306.

Builders think of it as two tatami mats, since a mat is half a tsubo, and some sources also count it as 10 go. In farming contexts the same area is sometimes called a bu. A tsubo is a very small plot, so larger land is quoted in multiples such as the se, tan and cho.

The unit travelled with Japanese rule. Korea's pyeong and Taiwan's ping are the same 3.3058 square metres. South Korea formally banned the pyeong in 1961 and made commercial use an offence in 2007, yet it persists informally, much as Japan kept the tsubo after metric units became the legal standard.

1 tsubo = 3.305785124 square meters (approximately).

Sources: Wikipedia: Tsubo; Wikipedia: Japanese units of measurement; Wikipedia: Shaku (unit)

Related conversions

See all area units.