How to use the acreage calculator
Pick the shape that matches your land and type its sizes. A rectangle needs a length and a width. A triangle can be a base and a height, or its three sides. A trapezoid needs its two parallel sides and the distance between them. For a lot with four straight sides, type the four sides in order and one diagonal, or type the corners as x and y points. If you already know the area, there is a shape for that too. Add every parcel and the page adds them up. The answer leads with acres (hectares in Metric) and shows square feet, square yards, square meters and square miles beside it, with the land drawn to scale.
The formula
Find the area in square feet, then divide by 43,560. Measure in feet and the arithmetic is one step. The areas come from the usual formulas: length × width for a rectangle, base × height ÷ 2 for a triangle, the two parallel sides added, halved and multiplied by the distance between them for a trapezoid, and π × diameter² ÷ 4 for a circle.
A worked example
A lot is 200 feet wide and 300 feet deep. Its area is 200 × 300 = 60,000 square feet. Divide by 43,560 and you get 1.377 acres, which is 1 acre plus 16,440 square feet. In metric, a lot 60 meters by 100 meters is 6,000 square meters, which is 0.6 hectare or 1.483 acres. Those are the numbers the page opens with, and the picture shows one whole acre square and a dashed square filled about 38 percent for the rest.
Lots that are not rectangles
Split the lot into triangles and rectangles and add the parts, or let the page do it: press a shape under Add another shape and it joins the list. A rectangle plus a triangle, an L made of two rectangles, or six pieces all work, up to twelve shapes. Tick Take this away on a shape that is inside the lot but not part of it, such as a house, a pond or an easement, and its area comes off the total. The shapes are separate pieces and the page does not check how they sit against each other. With three sides it uses Heron's formula and tells you when they cannot close into a triangle. With four sides and a diagonal it adds the two triangles the diagonal makes; the diagonal must run inside the lot, from the corner between sides 4 and 1 to the corner between sides 2 and 3. With corners it uses the shoelace formula: list them in order around the edge, either direction. If two sides cross, the page refuses the shape, because that number is not a land area. This is plane area from the numbers you type, so slope and survey corrections are outside it.
What an acre is
An acre is 43,560 square feet, or 4,840 square yards. The old surveyor's chain is 66 feet and a furlong is 660 feet, and an acre is one chain by one furlong, so it is also 10 square chains. A square mile is 640 acres. Since the international foot became exactly 0.3048 meter in 1959, an acre is exactly 4,046.8564224 square meters, about 0.4047 hectare. The US survey foot differs from the international foot by 2 parts per million and was set to be retired at the end of 2022; it makes a survey acre about 4 parts per million bigger, so the page uses the international foot. A square acre is about 208.7 feet on each side, and fencing it takes about 834.8 feet.
What it looks like
An American football field, end zones included, is 360 feet by 160 feet according to the NFL rulebook. That is 57,600 square feet, or about 1.32 acres. So the field is a little bigger than an acre, and a quarter-acre lot is about a fifth of it. The picture draws a dashed 1-acre square and, for land between 0.3 and 20 acres, a football field at the same scale as your land.
Lots and fences
The Lots and fences tab divides land by a lot size to show how many lots fit and what is left over. It counts plane area only: roads, setbacks and zoning are outside it. It also shows the most area a length of fence can hold, and the fence a square acre needs.
Where the numbers come from
The acre, the chain, the furlong and the foot at 0.3048 meter are definitions. The only measured numbers are the sizes you type, so the answer is only as good as your tape or your map. NIST's conversion tables list the US survey acre at 4,046.873 square meters, and the international acre follows from the foot. The football field size comes from the NFL rulebook. Land is sold and recorded by survey, so a plat or deed controls, and tax acreage and deed acreage can differ. Use this page to plan and compare, and a licensed surveyor for a boundary.
What people use it for
- Checking a listing's acreage against your own measurements.
- Pricing seed, mowing or fencing by the acre.
- Comparing parcels in acres, hectares and square meters.
Common mistakes
- Dividing by 43,560 when the sizes are in yards or meters. Convert to feet first, or type the unit and let the page convert it.
- Using the frontage times the deepest point. A lot that narrows or bends is smaller than its bounding box.
- Mixing up the diagonal. It must join opposite corners and stay inside the lot.
- Listing corners out of order. Go around the edge, one corner after the next.
- Treating the answer as a survey. It is only as exact as the numbers typed.
Questions
How many square feet are in an acre?
43,560. That is 4,840 square yards, or a square about 208.7 feet on a side.
How do I find the acres of an odd-shaped lot?
Use four sides and a diagonal, or type the corners in order. The page splits the lot into triangles or uses the shoelace formula. It refuses a shape whose sides cross.
Can I add a triangle to a rectangle?
Yes. Start with the rectangle, press Triangle under Add another shape, and type its base and height. The total is the two areas added. To subtract something inside the lot, like a house or a pond, tick Take this away on that shape.
How do I get the size from the map?
Open the free map tool, choose Just the acreage, and tap around the land on the aerial photo. The tool's result has a button that brings the area back here, where you can add or take away shapes.
Is this the same as a survey?
No. It works out plane area from the sizes you type. A survey measures the real boundary, and the deed or plat controls. Use a licensed surveyor for a boundary or a sale.
How many acres is a football field?
About 1.32. The field with its end zones is 360 by 160 feet, which is 57,600 square feet.
Can I use metric?
Yes. Press Metric to type meters and see hectares first, with acres beside them. The page opens in the system your browser's region uses and remembers your choice on this device.
Can I share my result?
Yes. Share makes a link with a picture for Facebook, a link you can copy, and a short video for TikTok made on your device. The link keeps only the shapes and their sizes, for 90 days.