Acres, Hectares and Square Miles: Land Area Units Compared
Land is sold, taxed and mapped in units that differ between countries. In the United States, property is usually described in square feet and acres. Much of the rest of the world uses square meters and hectares. Mapping and statistics often switch to square kilometers or square miles for large areas.
This guide shows how these units connect, gives the exact factors, and explains why converting an area is not the same as converting a length.
What each unit means
- Acre: 43,560 square feet, which is 4,046.86 square meters. Historically it is a strip one furlong long (660 ft) and one chain wide (66 ft). An acre as a square would measure about 208.7 feet, or 63.6 meters, on each side.
- Hectare: exactly 10,000 square meters, the area of a square 100 meters on each side. It equals 2.471 acres.
- Square mile: 640 acres, which is 2.59 square kilometers.
- Square kilometer: 100 hectares, or 247.1 acres.
| Unit | Square meters | Acres | Hectares |
|---|---|---|---|
| 1 acre | 4,046.86 | 1 | 0.4047 |
| 1 hectare | 10,000 | 2.4711 | 1 |
| 1 square kilometer | 1,000,000 | 247.11 | 100 |
| 1 square mile | 2,589,988 | 640 | 259.0 |
Worked examples
A 2.5 acre lot. In square feet that is 2.5 × 43,560 = 108,900 ft². In square meters it is 2.5 × 4,046.86 = 10,117 m², which is 1.012 hectares.
A 3.2 hectare field. Multiply by 2.471 to get 7.91 acres.
A town of 12 square miles. That is 12 × 640 = 7,680 acres, or 12 × 2.59 = 31.1 square kilometers.
A house plot of 80 ft by 120 ft. The area is 9,600 ft². Dividing by 43,560 gives 0.22 acres, and multiplying by 0.0929 gives 892 m².
The acres to hectares converter, the square feet to acres converter and the area converter cover these steps and more.
Prices and rates per area
A rate per unit of area moves the opposite way to the area. Because a hectare is a bigger unit than an acre, a price quoted per hectare is a bigger number than the same price per acre. Multiply by 2.471 to go from per acre to per hectare, and divide by 2.471 to go back.
Worked example: land priced at 8,000 per acre costs 8,000 × 2.471 = 19,768 per hectare. A crop yield of 5 tonnes per hectare is 5 ÷ 2.471 = 2.02 tonnes per acre. Multiplying where you should divide, or the reverse, is the most common slip with rates, and it leaves the answer wrong by a factor of 2.471 squared, about 6.1.
A check that catches the error: if the new unit is larger, the number per unit must get larger for a price, and smaller for a count of items divided across the area.
Reading a land listing
- Look for the unit first. A US listing for a rural parcel that says '2' normally means 2 acres, while small city lots are usually given in square feet.
- Compare listings in one unit. Convert everything to acres or hectares before judging price per area.
- Gross area can include land that cannot be built on or used, such as wetland, steep slopes or road easements. The usable area can be much smaller than the stated total.
- The figure on the deed or a recent survey is the authority. Online listings and maps are estimates.
Why you cannot reuse the length factor
One meter is 3.28084 feet, but one square meter is 3.28084 × 3.28084 = 10.764 square feet. An area unit is a length unit squared, so its conversion factor is also squared.
1 m² = 3.28084² ft² = 10.7639 ft²
Worked example: a room of 500 m² is 500 × 10.764 = 5,382 ft². Using the length factor by mistake gives 500 × 3.28 = 1,640 ft², which is about a third of the right answer. The same logic applies to volumes, which use the cube; the article on cubic feet, cubic yards and cubic meters shows it for job quantities.
Quick estimates and their errors
| Conversion | Shortcut | Error |
|---|---|---|
| Hectares to acres | × 2.5 | +1.2% |
| Acres to hectares | × 0.4 | −1.2% |
| Square miles to km² | × 2.6 | +0.4% |
| m² to ft² | × 11 | +2.2% |
| ft² to m² | ÷ 11 | −2.1% |
For example, 8 hectares is about 8 × 2.5 = 20 acres (exact 19.77), and 5 acres is about 5 × 0.4 = 2 hectares (exact 2.02). These are fine for judging scale. For anything legal, financial or measured on a survey, use the exact factors and the figures printed on the deed or plan.
This article is general information on unit conversion, not legal, surveying or property advice. Boundaries, taxes and sale prices depend on official records.
- Acres to Hectares Converter: Enter an area in acres and the equivalent in hectares appears immediately. Below you will find the exact factor, the reverse rule for hectares to acres, worked examples and a table of common sizes.
- Square Feet to Acres Converter: Enter an area in square feet and the number of acres is shown at once. The guide explains the divisor, gives lot-size examples and lists the square footage of familiar fractions of an acre.
- Area Converter: Pick a unit on each side, type an area and the converted value appears straight away. The guide lists the exact size of every unit in square meters, with worked examples and the mistakes to avoid.
This article is general information, not professional advice. See our Disclaimer and Editorial Policy.
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