A 100 × 120 ft lot is 12,000 square feet — 0.2755 acre, 1,333 square yards, 1,115 square meters or 0.1115 hectare. The calculator above turns the sides of a lot into acres, and converts any area between acres, square feet, square yards, square meters, hectares and square miles: type into any field and the rest follow.
How the calculator works
Choose the shape — rectangle, quadrilateral or triangle — and enter its sides. The area appears in every unit, and the drawing shows the lot on a grid of square chains, each a tenth of an acre. To convert a number you already have, type it into the field of its unit.
Where the acre comes from
An acre is the area of a strip one furlong (660 ft) long and one chain (66 ft) wide: 43,560 square feet. A square chain, 66 × 66 ft, is a tenth of an acre, which makes the grid a quick way to see acreage by eye.
| Area | Acres | Square feet | Hectares |
|---|---|---|---|
| Quarter-acre lot | 0.25 | 10,890 | 0.101 |
| Half-acre lot | 0.5 | 21,780 | 0.202 |
| Acre | 1 | 43,560 | 0.405 |
| Hectare | 2.471 | 107,639 | 1 |
| Square mile (section) | 640 | 27,878,400 | 259 |
Lots that are not rectangles
A triangle by its three sides uses Heron's formula. A four-sided lot needs a diagonal too — four sides alone can enclose very different areas — and is split into two triangles. For lots with more corners or to draw the shape by hand, use the lot size calculator.
Common mistakes
- Dividing by 43,000 or 45,000. It is 43,560.
- Mixing square feet and square yards. A square yard is 9 square feet.
- Four sides without the diagonal. The area is undetermined.
For lots of any shape, use the Lot Size Calculator; for a room, the Square Footage Calculator.