Area Calculator

Calculate the area of a rectangle, triangle or circle. Select a shape and enter its dimensions in the same unit to get the area in square units.

Choose a shape and enter dimensions

The calculator only uses the dimensions required for the selected shape.

units
units
Your result

Calculated area

Updates automatically as you change the inputs.

Area
80 square units
ShapeRectangle
Formula usedlength × width

How to use the area calculator

Choose the shape, then enter the requested dimensions using the same unit. The result is expressed in square units because area measures a two-dimensional surface.

Area formulas

Calculation formulaArea formulas
Used for the result above
Rectangle: A = length × width. Triangle: A = ½ × base × height. Circle: A = π × radius².

If the dimensions are in feet, the result is square feet. If they are in inches, the result is square inches.

Example: Zoe measures a circular space

Zoe measures a circle with a radius of 5 meters. Area is π × 5² = 25π, approximately 78.54 square meters.

If the measurement is the diameter, divide it by two before entering the radius. Doubling the radius multiplies the area by four, because the radius is squared.

Use the correct dimensions for your shape

For a rectangle, multiply length by width. For a triangle, multiply base by perpendicular height and divide by 2. For a circle, multiply π by radius squared.

A 10-by-8 rectangle has an area of 80 square units. If the dimensions are in meters, that means 80 m²; if they are in feet, it means 80 ft². Divide a circle's diameter by 2 before entering the radius.

How to calculate the area of an irregular room

Split an L-shaped room into rectangles, calculate each area and add the results. A 6-by-4 section plus a separate 3-by-2 section covers 24 + 6 = 30 square units. Avoid counting any overlap twice.

For a cutout, subtract its area from the enclosing shape. This tool directly supports rectangles, triangles and circles. For flooring measured in feet and inches, use the Square Footage Calculator.

Area unitEquivalent
1 square foot144 square inches
1 square yard9 square feet
1 square meterAbout 10.7639 square feet
1 acre43,560 square feet

Assumptions and limitations

What the estimate assumes

Complex or irregular shapes should be divided into simpler shapes or measured with a specialized tool.

Area Calculator FAQs

Why is area measured in square units?

Area describes two-dimensional space, so both dimensions contribute a unit factor.

What is the area of a rectangle?

Length multiplied by width.

What is the area of a triangle?

One-half times base times perpendicular height.

What is the area of a circle?

Pi times the radius squared.

General geometry calculator. Use consistent units for all dimensions.