Area Calculator
Work out the area of a room, floor, garden or wall in square feet or square metres from its length and width.
Area
20 m²
Please note: The result is an estimate and has been rounded. Actual costs and values may differ, and no rights can be derived from this calculation.
How this number is calculated
The blocks use your input. Change a value above and they update with it.
Step 1 · Area in square metres
Step 2 · Area
How the calculation works
Work out the area of a room, floor, garden or wall. Enter the length and width in feet, inches, metres or centimetres, and see the area in square feet or square metres.
The area of a rectangle is its length times its width. The calculator first converts both measurements to metres, multiplies them and gives the result in square metres (m²) or square feet (sq ft), whichever you choose. For a space that is not rectangular, split it into rectangles, work out each one and add them up.
Formula
Area = length × width. 1 sq ft = 0.09290304 m²; 1 m² = 10.764 sq ft.
Assumptions
- The room or surface is rectangular, with square corners.
- Length and width are inside measurements, from wall to wall.
- The result is rounded to two decimals.
Example calculations
The button fills in the calculator above, so you can carry on from there.
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Room
Area
20 m²
Length 5 m · Width 4 m · m²
-
Garden
Area
96 m²
Length 12 m · Width 8 m · m²
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Bathroom in centimetres
Area
5.88 m²
Length 280 cm · Width 210 cm · m²
Frequently asked questions
How do I work out the square footage of a room?
Measure the length and width from wall to wall and multiply them. A room of 12 by 10 feet is 12 × 10 = 120 square feet. If you measure in inches or metres, the calculator converts for you.
How do I measure an L-shaped room?
Split the room into two rectangles, work out the area of each part and add them together. The same works for any shape made of rectangles.
How much flooring should I buy?
Buy more than the area: some material is lost when cutting. An extra 5 to 10% is common advice, more for tiles laid diagonally or a room with many corners. The box says how much area it covers.
How do I work out the area of a circle or triangle?
A circle: π × radius × radius, where the radius is half the diameter. A circle 10 feet across is 3.14159 × 5 × 5 = 78.5 sq ft. A triangle: half of base × height.
How many square feet are in a square metre?
1 square metre is 10.764 square feet, and 1 square foot is 0.0929 square metres. Choose the unit you need under Result in; 20 m² is 215.28 sq ft.
Sources and checks
Sources
- NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement
- NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically
How we check it
This calculator has 9 fixed checks: 7 calculations with a result that is fixed in advance, and 2 cases of invalid input that must be rejected. They all run automatically every time we publish; if one fails, the calculator does not go live.
See the calculations
- Length 5 m · Width 4 m · m² → Area 20 m²
- Length 12 m · Width 8 m · m² → Area 96 m²
- Length 280 cm · Width 210 cm · m² → Area 5.88 m²
- Length 12 ft · Width 10 ft · ft² → Area 120 sq ft
- Length 5 m · Width 4 m · ft² → Area 215.28 sq ft
- Length 120 in · Width 96 in · m² → Area 7.43 m²
- Length 5 m · Width 0 m · m² → Area 0 m²
Changes
- : First version. Sources added and content reviewed.
Last reviewed: · How we build and check our calculators
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