How to use the Acreage Calculator
- Enter the plot dimensions in feet, metres or yards.
- For irregular plots, split the area into rectangles and triangles and add the results.
- Read the area in acres, hectares and square metres.
- Use a surveyed plan or title deed for anything legal or transactional.
How the calculation works
An acre is defined as 43,560 square feet, or 4,046.8564224 square metres, and a hectare is 10,000 square metres — about 2.471 acres. Rectangular plots are simply length × width converted into those units. Triangles use half base times perpendicular height, and irregular plots are best decomposed into simple shapes whose areas add, rather than approximated with an average width.
Land measured on the ground is horizontal area, and that is what deeds and area calculations use. A sloping field therefore has more surface than its recorded acreage, which matters for seeding, fencing and paving quantities even though the legal area is unchanged. For boundaries, a registered survey is the authority — hedge and fence lines commonly sit a metre or more off the recorded line.
1 acre = 43,560 ft² = 4,046.856 m² ; 1 hectare = 10,000 m² = 2.4711 acres ; triangle area = ½ × base × heightSource: International acre and hectare definitions per the 1959 international yard and pound agreement and SI derived units.
Worked example
A plot measuring 312 ft along the road, 268 ft deep on one side and 240 ft on the other, treated as a rectangle plus a triangle.
- Rectangle: 312 × 240 = 74,880 ft².
- Triangle: ½ × 312 × (268 − 240) = ½ × 312 × 28 = 4,368 ft².
- Total = 79,248 ft².
- Acres = 79,248 / 43,560 = 1.819.
About 1.82 acres, or 0.736 hectares — roughly 7,363 square metres.
Frequently asked questions
How many square feet are in an acre?+
Exactly 43,560 square feet, which is 4,046.856 square metres. A square acre is about 208.7 feet on each side.
How do I measure an irregular plot?+
Divide it into rectangles and triangles, calculate each area and add them. That is far more accurate than multiplying an average length by an average width, which systematically overstates awkward shapes.
Does slope change the acreage?+
Not the recorded acreage, which is horizontal area. The actual surface of a sloping site is larger, so seeding, fencing and surfacing quantities should be based on the slope distance.
Can I rely on this for a property transaction?+
No. Use the registered title plan or a licensed surveyor's measurement. Fence and hedge lines often differ from the legal boundary by a meaningful margin.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.