Geometry calculator
Area, perimeter and volume for everyday shapes.
- Answers as you type
- Runs entirely in your browser
- Free, no sign-up
Area = w × h Perimeter = 2(w + h)
Area
12 units²
Rectangle
- Perimeter
- 14 units
Units are whatever you type — centimetres in, square centimetres out. Convert first with the length converter if your measurements are mixed.
How it works
Choose a shape, type the measurements you have, and get the area or volume with the formula shown alongside. Handy for paint, flooring, soil, packaging or homework.
Example: A circle with a 2.5 m radius covers 19.63 m², and a 30 cm cube holds 27,000 cm³ — that is 27 litres.
Questions people ask
Which units should I use?
Any, as long as you stay consistent. Enter centimetres and the area comes back in square centimetres; enter metres and you get square metres.
How do I find the area of a triangle from three sides?
Heron's formula: halve the perimeter to get s, then take the square root of s(s−a)(s−b)(s−c). The calculator does this for you and warns if the sides cannot form a triangle.
How much paint or flooring do I need?
Work out the area, then add 10% for cuts and waste. For paint, multiply the wall area by the number of coats and divide by the coverage on the tin.
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