Area Calculator
Find the area of a room, a plot of land or any shape — and the tiles or paint you need.
Step by step
Your previous calculations
Tap one to open it again. Saved only on this device.
How it works
The method
Rectangle = length × width. Triangle = base × height ÷ 2. Circle = π × r². Box volume = length × width × height; cylinder = π × r² × h. Area units are squares of length units: 1 m² = 10,000 cm².
Worked example
A room 4 m by 3 m has an area of 12 m². A circle with radius 5 m has an area of 25π m² = 78.5398163397… m².
Common mistakes
Use the height at right angles to the base, not a sloping side. Put all lengths in one unit before multiplying: 1 m² is 10,000 cm², not 100 cm².
Questions & answers
How do I measure a room that is not a rectangle?
Split it into rectangles and triangles, work out each one, and add the areas. For an L-shaped room, that is two rectangles.
How do I measure land when I only know the sides?
Split the plot into triangles with straight lines between its corners, measure the three sides of each triangle, and use 3 sides (land). Add the triangles. The answer is also given in acres, hectares and decimals.
It says the sides can't make a triangle. Why?
Any two sides of a triangle together must be longer than the third. Check the measurements — one is probably too long or too short, or in a different unit.
Why does the circle's area end with …?
π never ends, so a circle's area doesn't either. The exact area is shown as a number × π, and the decimal shows only digits that are certain, followed by ….
How much extra should I add for tiles?
10 % is usual for straight laying and 15 % for diagonal laying or many cuts; follow your fitter's advice. The page always rounds up to whole tiles and whole boxes.
Where do I find the paint coverage?
It is printed on the tin, as m² per litre or ft² per gallon (often 10–12 m² per litre). Rough or new walls take more paint, so use the lower number.