Rectangle calculator
A rectangle's area is the product of its sides, its perimeter twice their sum, and its diagonal — by the Pythagorean theorem — the square root of the sum of their squares. Measure both sides in metres to get square metres.
m
m
Area
24m²
- Perimeter
- 20m
- Diagonal
- 7.211m
Rates and thresholds
- Area
- S = a × b
- Perimeter
- P = 2 × (a + b)
- Diagonal
- d = √(a² + b²)
How do I work out a room's square metres?
Measure length and width in metres and multiply: 4.2 × 3.5 metres gives 14.7 square metres. If the room is not rectangular, divide it mentally into rectangles, compute each and add them. Measuring in centimetres, divide the result by 10,000.
How much material should I buy per square metre?
Add an allowance to the calculated area for cutting waste and pattern matching: roughly a tenth for straight laying, more for diagonal or patterned material. Better over than under — buying more later can mean a different batch and a visible shade difference.
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