Tan to Square Kilometers (tan to km²)

1 tan equals 0.0009917355372 square kilometers (rounded).

1 tan = 0.0009917355372 square kilometers

How to convert tan to square kilometers

To convert tan to square kilometers, multiply the number of tan by 0.0009917355372. The factor is rounded to 10 significant digits. To go the other way, multiply square kilometers by 1,008.333333 (rounded).

square kilometers = tan × 0.0009917355372

Example: 10 tan = 0.009917355372 square kilometers.

About these units

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

Square Kilometer (km²)

Metric (SI)Current unit

One million square meters (100 hectares). Used for the area of cities, countries and lakes.

Metric land measure took a surprisingly long time to settle on the kilometer. The meter was defined in 1799, yet people initially preferred the myriameter, 10,000 meters, and the French phrase myriamètres par heure was still in print in 1802. The Netherlands adopted the kilometer in 1817 under the name mijl. Once the kilometer was established, the square kilometer followed naturally as the unit for areas too large to count comfortably in hectares or square meters.

One square kilometer is 1,000,000 square meters, or 100 hectares, about 0.3861 square miles or 247.1 acres. A useful picture comes from history: many medieval European cities were enclosed by walls around roughly a square kilometer, with Delft at about 0.9 km² and Lucca at about 1.09 km². A standard 18-hole golf course of 6,000 meters needs about 0.8 km². The symbol km² means the square of a kilometer, not a thousand square meters. The planned Square Kilometre Array radio telescope takes its name from the collecting area it aims for.

1 square kilometer = 1,000,000 square meters (exactly).

Sources: Wikipedia: Square kilometre; Wikipedia: Kilometres per hour

Related conversions

See all area units.