01What this calculator tells you
This calculator finds the area of a space in square meters (m²) — the SI derived unit of area, defined by the National Institute of Standards and Technology (NIST) as the area of a square one meter on each side. Choose a shape, pick the unit you measured in, and enter the dimensions. You get the area in m² plus instant conversions to square feet, square yards and hectares, a plain-language size reference, and an optional cost estimate.
It handles the three shapes that cover almost every real job: a rectangle or square (rooms, floors, walls, plots), a circle (patios, ponds, rugs) and a triangle (gables, corner plots). Measuring a run of pipe or cable instead of a floor? See our conduit fill calculator, or browse the full set on our calculators home page.
02Converting other units to square meters
The catch that trips people up is that area units are squared. There are 100 centimeters in a meter, but 100² = 10,000 square centimeters in a square meter. The table below shows what to multiply your area by once you have measured — or you can skip the arithmetic entirely and just set the unit selector.
03How big is a square meter, really?
A single square meter is easy to picture — about the footprint of a small bistro table. Areas get harder to imagine as they grow, which is why the calculator gives a real-world size reference alongside the number. The table below anchors a few common spaces so your result has context.
For land and very large areas, a hectare (ha) is 10,000 m², which is why the result panel reports hectares too. NIST publishes the full set of SI units if you want the formal definitions behind these figures.
- Pick the shape that best matches the space (rectangle/square, circle or triangle).
- Choose the unit you will measure in — the result is always returned in m² regardless.
- Measure the length and width (or diameter, or base and height) and enter them.
- Set the number of identical areas if you have several the same size, then press Calculate.
For an irregular room, split it into rectangles and triangles on a sketch, work out each piece, and add the areas together. The NIST guide to length units is a handy reference if you need to double-check a conversion first. Want your own number? Enter your values in the calculator and hit Calculate.
- It measures flat area only. For paint or plaster you often need wall area (height × width) rather than floor area, and you may subtract doors and windows.
- Add a waste allowance for materials. Flooring, tiles and turf are usually bought with 5–10% extra for cuts and offcuts; the raw m² is the starting point, not the order quantity.
- Circles use the diameter. Enter the full width across the circle, not the radius — the calculator halves it for you.
- Triangles need the perpendicular height. That is the straight-line height to the base, not the length of a sloping side.
- Cost is an estimate. The price-per-m² figure ignores delivery, labour and waste; treat it as a ballpark.
04Related calculators
Working through a related project? Try our Volume of a Triangular Pyramid Calculator, Stud Calculator, and Board and Batten Calculator.
01The square meter formula
Square meters measure a two-dimensional area, so every formula multiplies two lengths that have first been converted to meters. Pick the line that matches your shape.
Where:
- A= the area in square meters (m²).
- length / width= the two sides of a rectangle, in meters.
- diameter= the distance straight across a circle; the radius is half of it.
- base / height= the base of a triangle and its perpendicular height, in meters.
02Worked example
Say you measured a rectangular living room in feet — 16 ft by 12 ft — and want the area in square meters. Work it one line at a time:
So a 16 ft × 12 ft room is about 17.84 m² (192 sq ft) — roughly one and a half car parking spaces. Add a 10% waste allowance and you would order flooring for about 19.6 m².