Square Footage and Area Calculator.
Measure rooms, L-shapes, circles and walls, add them up, and take doors and windows back off. Shows the arithmetic for every segment.
Running total
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Put in a measurement and the total appears here.
Room 1
Length times width. The ordinary room.
Naming it is what makes the total checkable later.
Feet and inches can be typed into any field whatever this is set to.
Enter a measurement.
Enter a measurement.
Four identical bedrooms can be measured once and counted four times.
Doors and windows to subtract
Optional. Trade practice is to deduct the large openings and leave small windows in, because cutting in around a frame uses up the difference.
Preset sizes are the commonly stocked US nominal sizes, and every one of them can be edited.
Totals, waste and material
Set the unit the breakdown is shown in, add an allowance for offcuts, and work out how much material the area needs.
Trade rules of thumb: about 10% for a straight lay, 15% where a pattern has to be matched, 20% for a diagonal lay or a cut-up room.
Paint, sealer, flooring, wallpaper — or loose material such as mulch and gravel, which is sold by volume.
No defensible answer
Nothing has been measured yet. Add a segment and put in its measurements, and the total will appear here.
How this is worked out
- Foot to metre
- 1 ft = 0.3048 m exactly, so 1 ft² = 0.09290304 m² and 1 m² = 10.7639 ft².Source: International yard and pound agreement, 1959.
- Yard to foot
- 1 yd = 3 ft exactly, so 1 yd² = 9 ft² exactly.Source: International yard and pound agreement, 1959.
- Rounding
- Areas under 10 are shown to two decimal places, under 100 to one, and above that to the nearest whole unit. Every total is worked out at full precision first and rounded once, at the end — so a rounded segment total and the overall total can differ by a fraction of a unit.
- Feet and inches
- Inches are converted by dividing by 12. 12′ 6″ is read as 12.5 ft, and a bare second number after feet — 12′ 6 — is read as inches.
- Openings
- Doors and windows are subtracted as plain rectangles, width by height, from the surface named beside them. Where the openings add up to more than the surface itself, that segment is counted as zero rather than as a negative area.
Opening sizes are nominal US residential sizes and vary by builder, age of the property and region. Every preset here is editable — measure the actual opening whenever the number matters.
Waste allowances are trade rules of thumb, not measurements. They cover offcuts, breakage and the piece you get wrong. Where a material is hard to reorder in the same batch, installers commonly order at the top of the range.
How rooms are measured
Six things that decide whether the number is right
- Measure the long way and the short wayRun the tape along the floor rather than at waist height, and measure wall to wall rather than baseboard to baseboard where the number is being used to order material. Write down feet and inches as they are read — there is no need to convert anything.
- Break an awkward room into shapes that can each be measuredAn L-shaped room is a rectangle with a corner missing. A bay window is a half circle or a trapezoid. A room with one angled wall is a rectangle plus a triangle. Any room can be cut into pieces, and each piece stays checkable on its own.
- Name every piece before adding itA total with no names behind it cannot be checked a week later, and cannot be argued with. Named segments are the difference between a number and a measurement.
- Add the walls only when the walls are what is being coveredFlooring, carpet and tile need the floor. Paint and wallpaper need the perimeter times the ceiling height. Ceiling paint needs the ceiling, which for a rectangular room is the same area as the floor.
- Decide what to subtract, and say whichCommon trade practice is to deduct the large openings — a doorway, a slider, a picture window — and to leave small windows in, because cutting in around a frame uses up the difference. Where a number is being checked rather than ordered against, deduct everything and note that it was done.
- Add the waste allowance last, and keep it separateThe measured area and the amount to order are two different numbers. Keeping them apart is what makes it possible to compare a measurement against somebody else’s.
Common questions