Area

How it is calculated

An area unit is the square of a length unit, so the factor is squared too: 1 ft = 0.3048 m, so 1 ft² = 0.3048² = 0.09290304 m².

1 a = 100 m² (a square 10 m on a side), 1 ha = 100 a = 10,000 m² (100 × 100 m), 1 km² = 100 ha. 1 acre = 4046.86 m², a little over 0.4 ha; 1 square mile = 640 acres.

Keep in mind

• A fanega of land was the area sown with one fanega of grain, so it depended on the district and soil quality: roughly 3000 to 7000 m². The Castilian fanega de marco real is 6439.56 m². Check the local value in old documents before using it.
• Common mistake: converting the side instead of the area. A plot of 100 × 100 ft is not 30.48 m² but 30.48 × 30.48 = 929 m².