Area Calculator
Find the area of 11 shapes with the formula, working and unit conversions.
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How to use this calculator
Choose a shape, choose your units (mm, cm, m, km, in, ft, yd or mi), then enter the measurements. The area is calculated with the formula shown, and also converted to square metres, square feet, acres and hectares where useful.
How it's calculated
Each shape has its own formula, for example rectangle A = l × w, triangle A = ½ × b × h, circle A = πr², trapezium A = ½(a + b)h. For a triangle with three known sides, Heron's formula is used: A = √(s(s − a)(s − b)(s − c)) where s is half the perimeter.
Worked example
A rectangle 8 m long and 5 m wide has area 8 × 5 = 40 m². A circle with radius 7 cm has area π × 7² ≈ 153.94 cm².
Frequently asked questions
What is the difference between area and perimeter?
Area is the space inside a shape, measured in square units. Perimeter is the distance around the edge, measured in ordinary units.
Why are the units squared?
Area counts squares. If the sides are in metres, the area is in square metres (m²).
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Last updated October 2026. Results are for learning and guidance; always check important work. Calculations run in your browser and are not stored.