This area calculator covers rectangles, triangles, circles, and trapezoids, switching the input fields automatically when you change shape.
Math
Area Calculator
Calculate the area of a rectangle, triangle, circle or trapezoid.
Calculator
About this calculator
Formula notes
Rectangle A = w·h; triangle A = ½·base·height; circle A = πr²; trapezoid A = ½(a + b)·h. The page shows only the fields the selected shape needs.
Worked examples
- Example: a rectangle 5 × 4 units returns area 20 square units, matching the page default calculation.
- A trapezoid with parallel sides 8 m and 14 m and perpendicular height 5 m has area (8 + 14) x 5 / 2 = 55 m2.
How to use it
- Pick the shape from the selector first.
- Enter the sides or radius the shape requires.
- Read the area in square units of your inputs.
Frequently asked questions
Can I mix units like meters and centimeters?
No. Keep every input in the same unit; the result is that unit squared.
Which trapezoid sides are base a and base b?
They are the two parallel sides; enter the height as the perpendicular distance between them.
Limits and interpretation
- The selected formula assumes the dimensions describe the stated ideal shape; irregular boundaries need decomposition or surveying.
- All lengths must use one unit before calculation, and the result is expressed in that unit squared.