Updated
Math
Area Calculator
Calculate area for popular 2D shapes: rectangle, square, triangle (two methods), circle, trapezoid, parallelogram, ellipse, regular polygon, circle sector, and annulus (ring). Includes step-by-step working and unit-friendly results.
Tip: Use the same unit for every length input (cm, m, in, ft). Area outputs are always in square units (cm², m², in², ft²).
Choose a Shape to Calculate Area
Pick a tab, enter your dimensions, and calculate. The calculator shows the formula and the computed steps.
Area is measured in square units. Keep all lengths in the same unit for correct results.
A = l × w
A = s²
Tiles, flooring, land plots, square panels.
Base & height: A = (b × h) / 2
Heron: A = √(s(s−a)(s−b)(s−c)), where s = (a+b+c)/2
Heron: A = √(s(s−a)(s−b)(s−c)), where s = (a+b+c)/2
A = πr² | If diameter is given: r = d/2
A = (a + b) × h / 2
A = b × h
Use the perpendicular height, not the slanted side length.
A = πab
If you have full axes lengths, divide each by 2 to get a and b.
If n and side length s: A = n·s² / (4·tan(π/n))
If apothem a is known: A = (Perimeter × a) / 2, where Perimeter = n·s
If apothem a is known: A = (Perimeter × a) / 2, where Perimeter = n·s
Degrees: A = (θ/360)·πr²
Radians: A = (θ/2)·r²
Radians: A = (θ/2)·r²
A = π(R² − r²)
Make sure outer radius R is larger than inner radius r.
| Shape | Area formula | Inputs | Notes |
|---|---|---|---|
| Rectangle | A = l·w | l, w | Most common area formula |
| Square | A = s² | s | Special rectangle |
| Triangle | A = (b·h)/2 or Heron | b, h or a, b, c | Heron works with 3 sides |
| Circle | A = πr² | r or d | r = d/2 |
| Trapezoid | A = (a+b)·h/2 | a, b, h | a & b are parallel sides |
| Parallelogram | A = b·h | b, h | Use perpendicular height |
| Ellipse | A = πab | a, b | a and b are semi-axes |
| Regular polygon | A = n·s² / (4·tan(π/n)) | n, s | Or A=(Perimeter·apothem)/2 |
| Sector | deg: (θ/360)πr² | rad: (θ/2)r² | r, θ | Choose degrees/radians |
| Annulus | A = π(R² − r²) | R, r | Outer radius must be larger |