Calculators
Area Calculator
Pick a shape, type its measurements and get the area with the worked formula, converted to every common unit from square inches to acres and hectares.
A = l × w
Calculated on your device — nothing is sent anywhere. Diagrams are schematic.
Works in your browser. No account needed.
Frequently asked questions
How do I find the area of an irregular shape?
Divide it into shapes that have formulas — rectangles, triangles, trapezoids and circle sectors cover almost any outline — then add their areas. Pick “Irregular shape”, enter each part, and mark cut-outs such as a column or a bay you are excluding as “Subtract”. The total updates as you type.
Which triangle method should I use?
Use base and height when you can measure straight up from one side to the opposite corner (A = ½ × b × h). If you only have the three side lengths, use Heron’s formula. If you know two sides and the angle between them, use A = ½ × a × b × sin(C). All three give the same answer for the same triangle.
How many square feet are in an acre, and square meters in a hectare?
An acre is exactly 43,560 square feet, or 4,046.8564224 square meters. A hectare is 10,000 square meters, about 2.471 acres. The calculator uses these exact defined values, and a square foot is exactly 0.09290304 m² because a foot is defined as 0.3048 m.
Why does converting units change the number so much?
Area scales with the square of the length unit. There are 12 inches in a foot, so there are 12 × 12 = 144 square inches in a square foot, and 3 × 3 = 9 square feet in a square yard. Converting the lengths first and then multiplying — which is what the calculator does internally — avoids the common mistake of dividing by 12 instead of 144.
What is the formula for the area of a regular polygon?
For n equal sides of length s, A = n × s² / (4 × tan(180° / n)). A regular hexagon with 2 m sides, for example, has an area of 6 × 4 / (4 × tan 30°) ≈ 10.39 m². The diagram redraws with the number of sides you enter.
Is my data sent anywhere?
No. All the arithmetic runs in your browser; nothing is uploaded or stored. The default units follow your browser’s language (feet in the US, meters elsewhere) and you can change them at any time.
About this tool
This area calculator covers the shapes that come up in homework, DIY and land measurement: rectangle (A = l × w), square (A = a²), triangle by base and height, by three sides (Heron’s formula) or by two sides and the included angle, circle (A = πr²), ellipse (A = πab), trapezoid (A = (a + b)/2 × h), parallelogram (A = b × h), circle sector (A = θ/360 × πr²) and regular polygon. A labeled diagram shows exactly which measurement goes where, and the result line repeats the formula with your numbers substituted so you can check the working or copy it into your notes.
Lengths can be entered in millimeters, centimeters, meters, kilometers, inches, feet, yards or miles, and the answer is shown in every common area unit at once: mm², cm², m², hectares, km², in², ft², yd², acres and square miles. Conversions use exact definitions — 1 inch = 25.4 mm, 1 foot = 0.3048 m, 1 acre = 43,560 ft² — so the numbers match what a surveyor or a unit converter would give. Inputs accept decimals with a point or comma and simple fractions such as 5 1/2.
Real outlines are rarely a single shape. The irregular-shape mode lets you build an area from any number of parts, each with its own shape, and subtract cut-outs. An L-shaped room is two rectangles; a lot with a curved corner is a rectangle plus a quarter-circle sector; a gable wall is a rectangle plus a triangle. Each part shows its own worked formula so you can spot a mistyped value quickly.
For flooring, tiling or paint, the dedicated square footage and paint calculators add waste allowances, costs and can sizes on top of the area. Whatever you are measuring, measure each dimension twice, keep every length in the same unit, and round only the final answer — rounding intermediate values is a frequent source of error in hand calculations.