Area Calculator
Find the area of a rectangle, triangle, circle, trapezoid or eight other shapes, with the formula shown. Add up several shapes or subtract one, enter feet and inches together, and convert the total to square feet, square meters, yards or acres. For irregular shapes, enter the corners.
Area calculator
Pick a shape, enter its measurements, and add more shapes to total several areas (or subtract one, such as a pool from a lawn). In feet you can also enter inches.
Area of any polygon from its corners
Enter the corners in order around the shape (x and y in any one unit). The calculator uses the shoelace formula, which works for any shape with straight sides that don't cross. The example is an L-shaped yard: 1,225 square units.
| Corner | x | y |
|---|
Area formulas
| Shape | Area |
|---|---|
| Rectangle | length × width |
| Square | side² |
| Triangle | ½ × base × height, or Heron's formula from 3 sides |
| Circle | π × radius² (π ≈ 3.14159) |
| Ellipse | π × a × b (half the long and short widths) |
| Trapezoid | (base₁ + base₂) ÷ 2 × height |
| Parallelogram | base × height |
| Sector | π × r² × angle ÷ 360° |
| Regular polygon | n × s² ÷ (4 × tan(180° ÷ n)) |
| Any polygon | shoelace formula: ½ |Σ(xᵢ × yᵢ₊₁ − xᵢ₊₁ × yᵢ)| |
Converting area units
Area units convert by the square of the length factor. There are 12 inches in a foot, so a square foot holds 12 × 12 = 144 square inches, and a square yard holds 3 × 3 = 9 square feet. One square meter is 10.764 square feet, and an acre is 43,560 square feet.
Measuring a room for flooring, with waste and boxes? Use the square footage calculator. Measuring land? Use the acreage calculator.
Common questions
How do I calculate area?
Multiply length by width for a rectangle. A 12 ft by 15 ft room is 180 square feet. Other shapes have their own formulas, shown above.
How do I find the area of an irregular shape?
Split it into rectangles and triangles and add them, or enter its corners in the polygon box, which uses the shoelace formula.
How do I calculate the area of a circle?
π × radius². A circle 10 ft across has a radius of 5 ft, so its area is 3.14159 × 25 = 78.54 sq ft.
How many square feet are in a square yard?
9, because a yard is 3 feet and 3 × 3 = 9.
How do I calculate the area of a triangle with only three sides?
Use Heron's formula: s = (a + b + c) ÷ 2, area = √(s(s − a)(s − b)(s − c)). Sides 3, 4 and 5 give an area of 6.
Sources
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General information, not financial, tax or legal advice. Check important numbers with the official source before acting on them.