Area Calculator
Area of a square, rectangle, circle, triangle, trapezoid, parallelogram or ellipse.
Area Calculator
| Area | 30.0000 |
| Shape calculated | triangle |
A triangle with base 10 and height 6 has an area of (10 × 6) ÷ 2 = 30 square units — exactly half of the 10-by-6 rectangle around it.
Area measures the surface a two-dimensional shape covers, in square units. Each shape has its own formula, but most of them reduce to some version of base times height — the circle and ellipse being the famous exceptions that bring in π.
Pick a shape and enter its dimensions: A is the side (square), length (rectangle), radius (circle), base (triangle and parallelogram) or first base (trapezoid) and first semi-axis (ellipse); B is the width, height or second measurement the shape needs; C is used only by the trapezoid, as its height.
The formula
Worked example
A triangle with base 10 and height 6 has an area of (10 × 6) ÷ 2 = 30 square units — exactly half of the 10-by-6 rectangle around it.
The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.
Frequently asked questions
Why is a triangle's area half of base × height?
Because any triangle is exactly half of a parallelogram with the same base and height — draw a diagonal across a rectangle and the two triangles are identical, each covering half the area.
What units should the answer be in?
Whatever units you entered, squared. Dimensions in metres give square metres; in feet, square feet. Keep all dimensions in the same unit before calculating.
How do I get the area of an irregular shape?
Split it into rectangles, triangles and circles, calculate each part here, and add them up (subtracting any holes). Surveyors and flooring estimators use exactly this method.
Category: Math calculators
Related calculators
Perimeter Calculator
Perimeter of squares, rectangles, triangles and regular polygons, plus circumference.
Circle Calculator
Diameter, circumference and area from a circle's radius.
Triangle Calculator
Triangle area from base and height, or area and perimeter from three sides (Heron).
Square Footage Calculator
Area in square feet and square meters for rectangles, triangles, circles and trapezoids.