Index / MATH CALCULATORS
An area calculator finds the area of five common shapes: rectangle, square, circle, triangle and trapezoid. Pick the shape, enter its dimensions, and read the area plus the perimeter or circumference where it applies. The formula used is printed under every result.
How to use it
- Pick the shape from the dropdown. The input fields change to match.
- Enter the dimensions in the same units (inches, feet, cm, whatever you use).
- Read the area in square units. Rectangles, squares and circles also show perimeter or circumference.
The formulas
Rectangle: A = length × width
Square: A = side²
Circle: A = π × radius²
Triangle: A = ½ × base × height
Trapezoid: A = ½ × (base1 + base2) × height
Square: A = side²
Circle: A = π × radius²
Triangle: A = ½ × base × height
Trapezoid: A = ½ × (base1 + base2) × height
Worked example
A rectangle 10 by 6:
Area = 10 × 6 = 60 square units
Perimeter = 2 × (10 + 6) = 32 units
Area = 10 × 6 = 60 square units
Perimeter = 2 × (10 + 6) = 32 units
Frequently asked questions
How do I find the area of a rectangle?
Multiply length by width. Both must be in the same units, and the answer comes out in square units.
What units does the area come in?
Square units of whatever you entered: square feet, square meters, square inches. Keep all inputs in the same unit.
How do I get a circle’s area from its diameter?
Halve the diameter to get the radius first, then use π × radius². Or enter the radius directly.