Square Kilometers to Ares (km² to a)

1 square kilometer equals 10,000 ares exactly.

1 square kilometer = 10,000 ares

How to convert square kilometers to ares

To convert square kilometers to ares, multiply the number of square kilometers by 10,000. This factor is exact. To go the other way, multiply ares by 0.0001.

ares = square kilometers × 10,000

Example: 10 square kilometers = 100,000 ares.

About these units

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

Are (a)

Metric (SI)Traditional unit (still used in some regions)

100 square meters, a square 10 m on a side. Mostly replaced by the hectare (100 ares).

Latin area, meaning an open piece of ground, gave French the word are, the base land unit of the metric system. A French law of 1795 defined it as 100 square meters, a square ten meters on each side, and the hectare was then built as 100 ares, which is why that familiar unit carries the "hecto-" prefix.

The are itself never made it into the modern SI when the system was rationalised in 1960, and the hectare took over for fields, forests and planning. The are survives mostly as a convenience for small plots such as building lots and gardens, and in everyday talk in parts of continental Europe. NIST lists it as exactly 100 square meters, so the figure used here is firm, and 100 ares make one hectare. The hectare is about 2.47 acres, so an are is roughly a fortieth of an acre.

1 are = 100 square meters (exactly).

Sources: Wikipedia: Hectare; NIST SP 811, Appendix B.8 conversion factors

Related conversions

See all area units.