Land is the oldest thing people have needed to measure fairly: for taxes, rent, inheritance and sale. The acre and the hectare, the two units used for land today, show two very different ways of doing it.
The acre: a day’s work
The word acre comes from the Old English æcer, a field. In medieval England it meant roughly the area a team of oxen could plough in a day. Ploughing in long strips was efficient, so the classic acre was a strip one furlong long (a “furrow long”, 660 feet) and one chain wide (66 feet).
660 × 66 gives the familiar figure: 43,560 square feet per acre. The chain itself was standardized in 1620 by the English mathematician Edmund Gunter as a surveyor’s chain of 100 links, so that 10 square chains make an acre and surveyors could calculate areas with decimals.
How the US was laid out in square miles
After independence, the US Public Land Survey divided much of the country into a grid. A township is 6 miles by 6 miles, split into 36 sections of one square mile each, and one square mile is exactly 640 acres. A quarter section, 160 acres, was the standard grant under the Homestead Act of 1862. Fly over the Midwest and you can still see the grid in roads and fields.
The hectare: a 100-meter square
The metric system of the 1790s introduced the are, a square 10 meters on a side (100 m²). The hectare, “a hundred ares”, is a square 100 meters on a side: 10,000 m². It is the standard land unit almost everywhere outside the US and the UK. Larger areas use square kilometers (100 hectares each).
Converting land areas
- 1 acre = 43,560 ft² = 4,046.8564224 m² (exact, using the international foot).
- 1 hectare ≈ 2.4711 acres, and 1 acre ≈ 0.4047 hectares.
- 1 square mile = 640 acres ≈ 259 hectares.
- An American football field including both end zones covers about 1.32 acres.
The area converter draws your area as a square to scale, tiled in both units and compared with familiar spaces from a parking space to Central Park. Because every area unit is a length unit squared, its accuracy rests on the exact foot described in where the inch, foot and mile came from.
Try it
- Length & distance converter — mm to miles, drawn on a dual ruler
- Area converter — square feet to acres, as a floor plan