Measurement tools
Area Calculator
Rectangles, circles, triangles and L-shapes, alone or added together.
How this calculator works
Pick a shape for each section of your space, enter its dimensions in metres and the calculator returns the area instantly. Add as many sections as you need and it keeps a running total.
Rectangles multiply length by width. Circles use pi times radius squared. Triangles take half of base times height, using the perpendicular height, not the sloped side. L shapes are handled as two rectangles.
Totals show in square metres with square feet alongside, so the result is ready for whichever units your supplier or plan uses.
| Shape | Formula | Example |
|---|---|---|
| Rectangle | length × width | 5m × 4m = 20m² |
| Circle | π × (diameter ÷ 2)² | 3m circle = 7.07m² |
| Triangle | ½ × base × height | 4m base, 3m height = 6m² |
| L shape | two rectangles added | 6×4 plus 2×2 = 28m² |
Frequently asked questions
How do I work out the area of an irregular shape?
Divide it into rectangles, triangles and circle parts, calculate each and add them up. This calculator does exactly that with its multiple sections.
Which height do I use for a triangle?
The perpendicular height: the straight line distance from the base to the opposite point, at right angles to the base. It is not the length of the sloping side.
How accurate do my measurements need to be?
Within a centimetre or two is plenty for home projects. Errors multiply though, so measure the longest dimensions most carefully.
Can I calculate a circle from its circumference?
Divide the circumference by pi (3.1416) to get the diameter, then enter that here. A tree ring measuring 6.28m around has a diameter of 2m.
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