Area Calculator
Instantly calculate the area and perimeter of squares, rectangles, circles, triangles, and trapezoids. Free, accurate tool for geometry, construction, and everyday measuring.
Calculate Your Shape’s Area
Choose a shape and enter its dimensions below to get an instant, precise area calculation, plus perimeter and the formula used.
Shape Details
Select a shape and enter its dimensions
Area Calculation
Calculated area, perimeter, and formula
Common Area Formulas
Standard area formulas for the most common shapes, so you can check your working or calculate by hand.
| Shape | Formula | Perimeter |
|---|---|---|
| Square | A = s² | P = 4s |
| Rectangle | A = l × w | P = 2(l + w) |
| Circle | A = πr² | C = 2πr |
| Triangle | A = ½ × b × h | P = a + b + c |
| Trapezoid | A = ½(a + b) × h | P = a + b + c + d |
Area Calculator FAQ
Everything you need to know about calculating area for common shapes.
The area of a rectangle is calculated by multiplying its length by its width. For example, a rectangle with a length of 8 and a width of 5 has an area of 40 square units.
The area of a circle is calculated using the formula π times the radius squared (A = πr²). For example, a circle with a radius of 4 has an area of approximately 50.27 square units.
The area of a triangle is calculated as half of the base multiplied by the height (A = ½ × base × height). For example, a triangle with a base of 10 and a height of 6 has an area of 30 square units.
The area of a trapezoid is calculated by adding the two parallel sides, dividing by two, and multiplying by the height (A = ((a + b) / 2) × h). This averages the two bases before applying the height.