Area Calculator

Work out the area of a rectangle, circle, triangle, and other shapes.

Runs in your browser — nothing is sent or saved.

How to use the area calculator

  1. Choose the shape.
  2. Enter the measurements it asks for.
  3. Read the area and the formula used.
  4. Copy the link to save or share it.

Area of common shapes

Area is the amount of flat space a shape covers, measured in square units. This area calculator handles the shapes that come up most: rectangle, square, triangle, circle, trapezoid, parallelogram, and ellipse. Pick one and it asks only for the measurements that shape needs, then shows the area of a shape and the formula so you can follow the working.

The formulas

Each shape has its own rule. The area of a rectangle is length times width. A triangle is half the base times the height. A circle is pi times the radius squared. A trapezoid is the average of its two parallel sides times the height. A parallelogram is base times height, and an ellipse is pi times its two semi-axes multiplied together. The tool fills in your numbers and shows the result.

Units and square footage

The area comes out in the square of whatever unit you put in, so entering feet gives square feet, which is how square footage is measured, and entering metres gives square metres. Keep all the measurements in the same unit. To convert an area to another unit afterwards, remember the factor is squared: one metre is about 3.28 feet, so one square metre is about 10.76 square feet.

A worked example

For a rectangle 8 by 5, the area is 8 times 5, which is 40 square units. For a circle with a radius of 3, the area is pi times 3 squared, which is pi times 9, about 28.27 square units.

FAQ

How do I find the area of a rectangle?

Multiply the length by the width. For 8 by 5, the area is 40 square units. Choose Rectangle and enter the two sides.

How do I find the area of a circle?

Square the radius and multiply by pi. For a radius of 3, the area is about 28.27 square units. Choose Circle and enter the radius.

What units is the area in?

Square units of whatever length unit you entered, so feet give square feet and metres give square metres. Keep every measurement in the same unit.

How do I find the area of a triangle?

Multiply the base by the height and halve it. If you only know the three side lengths, use the triangle calculator, which applies Heron's formula.

Is my information private?

Yes. Everything is calculated in your browser and nothing you enter is uploaded or saved.