Square footage calculator
Most rooms
aren't one rectangle.
Add every space, subtract what you're not covering, and get the number you actually need — boxes, gallons, yards or squares. Type dimensions the way you'd say them: 12'6", 12.5, or 150".
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How to measure square footage
Square footage is length × width. The arithmetic is never the hard part — breaking a real space into shapes is. Measure at the floor, not at eye level, and keep the tape flat against the baseboard so it doesn't read long.
L-shaped rooms
Don't try to average it. Split the room into two rectangles along the inside corner, measure each one, and add them. Or use the L-shape row above: measure the full outer width and length, then the bite taken out of the corner.
Things you shouldn't cover
Kitchen islands, base cabinets, a hearth, a built-in tub. Add them as removing rows. Most calculators can't subtract, so people order material for floor they'll never see.
Closets, bays and nooks
Each one is its own row. A 3 × 5 closet is 15 ft² — about one extra box of flooring. Four closets is most of a box you'd otherwise be short.
Why add a waste factor
Cuts, breakage and pattern matching mean you never install 100% of what you buy. 10% is standard for straight-lay flooring, 15% for diagonal or herringbone layouts, and more for busy rooms with lots of cuts.
Area conversions
| From | To square feet | To square metres |
|---|---|---|
| 1 square foot | 1 | 0.092903 |
| 1 square yard | 9 | 0.836127 |
| 1 square metre | 10.7639 | 1 |
| 1 square (roofing) | 100 | 9.2903 |
| 1 acre | 43,560 | 4,046.86 |
Common room sizes — quick reference
| Room | Typical dimensions | Typical area |
|---|---|---|
| Master bedroom | 14 × 12 to 20 × 16 | 168–320 ft² |
| Secondary bedroom | 12 × 10 to 14 × 12 | 120–168 ft² |
| Bathroom | 5 × 8 to 10 × 10 | 40–100 ft² |
| Kitchen | 10 × 10 to 15 × 12 | 100–180 ft² |
| Living room | 15 × 12 to 20 × 18 | 180–360 ft² |
| Dining room | 12 × 10 to 14 × 12 | 120–168 ft² |
| Garage (1-car) | 12 × 20 to 12 × 22 | 240–264 ft² |
| Garage (2-car) | 20 × 20 to 22 × 22 | 400–484 ft² |
| Closet (reach-in) | 3 × 3 to 4 × 3 | 9–12 ft² |
| Closet (walk-in) | 6 × 6 to 8 × 6 | 36–48 ft² |
Common questions
How do I calculate the square footage of an L-shaped room?
Divide it into two rectangles at the inside corner, find the area of each, and add them together. The alternative is to measure the full rectangle the room would be if the corner were filled in, then subtract that missing corner. Both give the same answer — use whichever is easier to reach with a tape.
Can I enter feet and inches?
Yes. 12'6", 12' 6, 12-6 and 12 6 are all read as twelve feet six inches. Fractions work too: 12' 6 1/2". Inches alone need a mark — 150" — and a bare number is read as feet. Whatever you type, the calculator echoes back how it read it, so an ambiguous entry can't quietly turn into a wrong order.
How many boxes of flooring do I need?
Multiply your square footage by one plus the waste factor, divide by the coverage printed on the box, then round up. A 320 ft² room at 10% waste is 352 ft²; at 22.5 ft² per box that's 15.6 boxes, so you buy 16. Buy the extra box from the same production run — dye lots shift between runs, and a repair two years from now won't match.
How much paint do I need for a room?
Paint covers walls, not floor, so floor area is the wrong input. Wall area is the room's perimeter times the ceiling height, minus the doors and windows. Switch to the Paint tab above and it does that from your ledger — a typical gallon covers about 350 ft² per coat, and most colours need two.
Is square footage measured inside or outside the walls?
It depends on why you're measuring. For materials you're buying — flooring, tile, paint — measure inside the finished walls, because that's the surface you're covering. For a listing or an appraisal, gross living area is normally measured to the outside of the exterior walls and follows the ANSI Z765 standard, which is why a listing's square footage is usually larger than the total of the rooms.
What counts as square footage in a house?
Finished, climate-controlled living space above grade counts toward gross living area. Basements that are fully finished may count depending on local standards and the appraiser. Garages, attics, porches, patios, and unfinished spaces typically do not count. This is why a "2,000 square foot" house might feel smaller than the number suggests — the garage isn't included, but it may be part of the building footprint.
How do I measure a triangle-shaped room?
Measure the base (the longest straight wall) and the height (the perpendicular distance from the base to the opposite corner). Multiply them and divide by 2. If the triangle is not a right triangle, the formula still works — you just need the perpendicular height, not the slanted side length.
How do I measure for hardwood flooring?
Measure the interior dimensions of each room at floor level. Add all rooms together, subtract permanent fixtures like kitchen islands and base cabinets, then add 10% waste for straight layouts or 15% for diagonal or herringbone. Ask your supplier what the manufacturer requires for acclimation — it depends on the product and on the moisture content of your subfloor, not on a fixed number of hours.
What is the difference between square footage and living area?
Square footage is the mathematical area of any space. Living area (or gross living area) is a real estate term defined by the ANSI Z765 standard — it includes only finished, climate-controlled space above grade with a ceiling height of at least 7 feet. A 2,000 ft² house might have 1,800 ft² of living area if the attached garage takes up 200 ft².
Does anything I type get sent anywhere?
No. Every calculation runs in your browser, and your ledger is saved only to this device's local storage so it's still here when you come back. There's no account, no upload, and no server holding your measurements. Clearing your browser data clears it. You can verify this by opening your browser's DevTools, going to the Network tab, and confirming there are zero outgoing requests while you use the calculator.
The rest of the toolbox
One measurement, then whichever material you're buying. Every tool reads the same ledger you just filled in.