How to Calculate Acreage — 3 Ways That Work

One acre = 43,560 square feet. Everything else is converting the shape you actually have — a clean rectangle, or the irregular real-world lot — into square feet and dividing. Here are the three practical methods.

Method 1: The rectangle formula (fastest, when it's square)

If the lot is a true rectangle, measure the two sides and divide:

acreage = (length ft × width ft) ÷ 43,560

Worked example: a 150 ft × 90 ft backyard = 13,500 sq ft ÷ 43,560 = 0.31 acres. Metric version: square meters ÷ 4,046.86 = acres.

In meters: length m × width m = square meters; divide by 4,046.86 for acres, or by 10,000 for hectares (1 hectare = 2.471 acres).

Method 2: Trace it on a map (for real, irregular lots)

Real properties are rarely rectangles. The area calculator handles any shape: click each corner of the lot on the map, drag to fine-tune, and the acreage computes live — in acres, square feet, hectares and more. It uses the same spherical-earth math that survey-grade GIS tools use, so it matches county records closely when the corners are placed accurately.

Best for: irregular lots, farmland fields, fencing estimates and checking a listing's advertised acreage against the map.

Method 3: Split odd shapes into rectangles

For an L-shaped or awkward lot without a map: sketch it on graph paper, split it into two or three rectangles, calculate each with the formula, and add them up. Old-school, but it works with just a tape measure — and it double-checks any digital result.

Quick conversion reference

Acres	Square feet	Square meters	Hectares
0.25 ac	10,890	1,012	0.10
0.5 ac	21,780	2,023	0.20
1 ac	43,560	4,047	0.40
2 ac	87,120	8,094	0.81
5 ac	217,800	20,234	2.02
10 ac	435,600	40,469	4.05
20 ac	871,200	80,937	8.09
40 ac	1,742,400	161,874	16.19

Frequently asked questions

How do I calculate the acreage of an irregular lot?

Trace the boundary on the map-based area calculator — click each corner of the lot and the acreage computes live using spherical-earth geometry. For manual work, split the shape into rectangles, calculate each, and add them.

How many square feet is 1 acre?

One acre is exactly 43,560 square feet — roughly a square 208.7 feet on a side, or about 70% of a soccer field.

How do I convert square meters to acres?

Divide square meters by 4,046.86. One hectare (10,000 m²) equals 2.471 acres.

Is a lot listed as 1 acre always exactly 1 acre?

Listings round. A '1-acre' lot may be 0.9 or 1.1 acres — check the plat or deed for the legal area, and measure the physical boundaries to compare.

Does the map method work for wooded or sloped land?

Map acreage is flat (planimetric) area — the horizontal footprint. Sloped terrain has more surface area than its map footprint, and tree cover doesn't change the boundary. For steep-slope surface area, a professional survey is the reliable route.

Page last updated November 6, 2026. Data sources and methodology are described in the sections above and in About.

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