Area Calculator

Pick a plane shape and enter its lengths in one unit. The result is area in that unit squared.

How it works

Area is length times length. A rectangle is lw, a square is s², a triangle is ½bh, a circle is πr², a trapezoid is ½(a+b)h, a parallelogram is base × height, and an ellipse is πab. Every input is a length; the output is an area.

Convert to one unit before you start so a cm side is never multiplied by an inch side.

Formula

Square: A = s²
Rectangle: A = lw
Triangle: A = ½bh
Circle: A = πr²
Trapezoid: A = ½(a + b)h
Parallelogram: A = bh
Ellipse: A = πab

Worked examples

A 5 by 3 rectangle
rectangle 5 × 3 → 15 unit²
A circle of radius 2
r = 2 → 4π ≈ 12.566 unit²

Useful notes

Triangle here is base and height only. Three-side solving lives on the triangle page.
Circle from diameter or circumference is on the circle calculator.

FAQ

How do I find the area of a rectangle?: Multiply length by width. 5 × 3 = 15.
What unit is the answer in?: The square of your length unit. Inches in, square inches out.
Is this the same as surface area?: No. This is a flat region. Surface area wraps a 3-D solid — use that page for cubes, cylinders and spheres.

Related tools

See all Geometry tools.