Square Footage Calculator

When to use it

Flooring, turf, membrane, roofing felt and paint all start with the same question: how big is this rectangle? This page takes a length and a width in the unit you actually measured in — metres, feet, inches, yards or centimetres — and returns the area in square metres, square feet and square yards, plus the perimeter.

It also prices the job when you enter a cost per square metre, which is how flooring and tiling are usually quoted. The area is for a rectangle; an L-shaped room needs to be split into two rectangles and added by hand.

How the maths works

Both dimensions are converted to metres first: one foot is 0.3048 m, one inch 0.0254 m, one yard 0.9144 m and one centimetre 0.01 m. Area = length × width in metres. One square metre is 10.7639 square feet and 1.19599 square yards, and the perimeter is 2 × (length + width) in metres.

Converting to metres before multiplying is what stops the classic error of mixing a centimetre with a metre inside the same rectangle.

A worked example

A room 5 m by 4 m.

1. Area: 5 × 4 = 20 m².
2. In square feet: 20 × 10.7639 = 215.28 ft².
3. In square yards: 20 × 1.19599 = 23.92 yd².
4. Perimeter: 2 × (5 + 4) = 18 m.

At 25 per square metre the same floor costs 500.00, which is the figure the optional price field adds.

Areas at a glance

One square foot is 0.0929 m², so a 120 ft² room lands just above eleven square metres — a useful check when a quote switches units.

Common mistakes

• Mixing units in one rectangle. A 300 cm by 4 m room is not 1,200 of anything until both sides share a unit.
• Confusing perimeter with area. The 18 m perimeter of the example has nothing to do with the 20 m² of floor.
• Buying the exact area. Cuts, breaks and pattern matching need a margin; order 10% extra for flooring and more for diagonals.
• Ignoring the price unit. A quote per square foot must be converted before comparing it with a price per square metre.

Keep exploring

• Area Converter — convert an area between metric and imperial units.
• Paint Quantity Calculator — turn a wall area into litres of paint.
• Tile Calculator — turn a floor area into tiles and boxes.