Acreage calculator
Show the working — with your numbers
Acres to a square lot
Plane geometry on the lengths you type: a rectangle, or two triangles by Heron’s formula. A lot with a curved or many-sided boundary needs more pieces, and the legal area of a property is whatever the survey or deed says — this is an estimate from your tape.
Type a rectangle’s length and width, or the four sides of an irregular lot plus one diagonal, and the tool gives the area in acres, square feet and square yards, and in hectares and square metres. The second calculator turns acres or hectares into the side of a square lot.
Worked example
Imperial: a 300 × 150 ft lot is 45,000 ft². 45,000 ÷ 43,560 = 1.03 acres (5,000 yd², 0.418 ha). An irregular lot with sides of 200, 180, 210 and 190 ft and a 280 ft diagonal: the first triangle (200, 180, 280) has s = 330 and area √(330 × 130 × 150 × 50) = 17,937 ft²; the second (210, 190, 280) is 19,945 ft². Total 37,882 ft², 0.87 acres.
Metric: a 100 × 50 m lot is 5,000 m² = 0.5 ha (1.24 acres). An irregular lot with sides 60, 55, 65 and 58 m and an 80 m diagonal: the two triangles are 1,649 m² and 1,861 m², total 3,510 m² — 0.351 ha, about 0.87 acres.
On the job
Break it into triangles. Any straight-sided lot can be split into triangles by diagonals from one corner. Run each four-sided piece here and add them. A five-sided lot is a four-sided piece plus one triangle: measure the triangle’s three sides, work it with Heron’s formula from the quick reference below, and add it on.
Acres for seed, fertiliser and spray. Rates on the bag are per acre or per hectare. A 0.87-acre lot at a rate for one acre takes 87% of it — round the product up, not the area.
Frontage × depth is not the area. A lot sold as “100 by 200” with a skewed back line can be several percent short of 20,000 ft². Measure all four sides and a diagonal before you believe the listing.
What went wrong?
Quick referencefor land area
- Acre
- 43,560 ft² = 4,840 yd² = 4,046.9 m² = 0.4047 ha
- Hectare
- 10,000 m² = 2.471 acres = 107,639 ft²
- Square lot
- one acre: 208.7 ft a side · one hectare: 100 m a side
- Bigger units
- square mile = 640 acres · km² = 100 ha
- Triangle (Heron)
- √(s(s − a)(s − b)(s − c)), s = half the perimeter
The formula
acres = square feet ÷ 43,560 · hectares = square metres ÷ 10,000
A rectangle is length × width. A four-sided lot is two triangles on the diagonal, each √(s(s − a)(s − b)(s − c)) where s is half its perimeter. The side of a square lot is the square root of its area.
Questions
- How many square feet are in an acre?
- An acre is 43,560 square feet — 4,840 square yards, about 4,046.9 m² or 0.4047 hectares. Going the other way, a hectare is 10,000 m², about 2.471 acres.
- How do I work out the acreage of a lot?
- For a rectangle, length × width in feet gives square feet; divide by 43,560 for acres. A 300 × 150 ft lot is 45,000 ft², 1.03 acres. In metric, length × width in metres gives square metres; divide by 10,000 for hectares — 100 × 50 m is 5,000 m², 0.5 ha.
- Why does a four-sided lot need a diagonal?
- Four sides alone do not fix the shape: the same four sides can lean like a gate that has lost its brace, and the area shrinks as it leans. One diagonal splits the lot into two triangles whose areas are fixed by their three sides (Heron’s formula), so the total is fixed too.
- How long is each side of a one-acre square lot?
- The square root of 43,560, about 208.7 ft — roughly 208 ft 8 1/2 in. A square hectare is exactly 100 m on a side. A lot twice as long as it is wide needs about 147.6 × 295.2 ft for one acre.
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