Square Metre Calculator

Quick answer Multiply length by width in metres: a 4 m by 3.5 m room is 14 square metres. For paint, carpet or tiles, add about 10 per cent for waste, and split L-shaped rooms into rectangles and add the pieces.
Quick answer: Square metres are length multiplied by width, both in metres. A room 5 m long and 4 m wide is 20 m². Enter a quantity as well to total several identical areas at once, or switch units to work in centimetres, millimetres or feet.

This calculator works out the area of a room, wall, section of land or any rectangular space in square metres, spelled square meters in American English, the measurement used for flooring, tiling, paint, turf, decking and council rates across New Zealand. Enter the length and width of the space, choose whether you measured in metres or centimetres, and if you have several identical areas, such as matching bedrooms or fence panels, add the quantity so you do not have to calculate each one separately. The calculator instantly returns the total area in square metres, the area per single space, and the number of areas you entered, updating live as you change any figure. Behind the scenes it simply multiplies length by width, converting centimetre measurements to square metres by dividing by 10,000. It is built for tradespeople quoting jobs, homeowners planning a renovation, and anyone ordering carpet, tiles, turf or paint who needs an accurate area before buying materials. Because most rooms are not perfect rectangles, split an L-shaped or irregular space into smaller rectangles, work out each one, and add the totals together for the true area. When you order materials, remember this figure is the raw area only, so add a wastage allowance, typically 5 to 10 percent for flooring and tiling, to cover cuts and offcuts, and check the coverage rate for paint or turf before buying.

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20 m²
total area
Per area20 m²
Number of areas1

How to calculate square metres

Area in square metres is length times width, with both measured in metres. If you measured in centimetres, multiply the two figures and divide by 10,000, because there are 10,000 square centimetres in a square metre. For several identical areas, work out one and multiply by the quantity.

Worked example

A lounge is 5 m long and 4 m wide. The area is 5 x 4, which is 20 square metres. If you were carpeting three rooms of that exact size, the total is 60 square metres.

For carpet or tiles, add about 10% for cuts and offcuts, so 60 square metres becomes about 66 square metres ordered.

Using the area for materials

  • Flooring and tiles: add 5 to 10% for waste and cuts.
  • Paint: divide the wall area by the tin's coverage (often 10 to 14 m² per litre per coat), and allow for two coats.
  • Turf or seed: use the area directly, then follow the product's coverage rate.

Frequently asked questions

How many square centimetres in a square metre?

10,000. So divide an area measured in square centimetres by 10,000 to get square metres.

How do I handle an L-shaped room?

Split it into rectangles, work out each rectangle, and add them together.

Who this calculator is for

This calculator is for anyone working out a floor, wall or land area in square metres, for flooring, paint, tiling or turf.

What this calculator assumes

  • The dimensions and units you enter.
  • A rectangular (length by width) area unless stated otherwise.
  • All dimensions are in consistent units.
  • Add a wastage allowance when ordering materials.

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