SQUARE FOOTAGE CALCULATOR
How it works
A room 12 ft long and 10 ft wide.
- Multiply length by width: 12 ft × 10 ft = 120 ft².
- Divide by 9 for square yards: 120 ÷ 9 = 13.33 yd².
- Divide by 43,560 for acres: 120 ÷ 43,560 = 0.0028 acres.
120 square feet — 13.33 square yards, or 11.15 square metres.
Constants
| Constant | Value |
|---|---|
| Square feet per acre | 43,560 ft² |
| Square feet per square yard | 9 ft² |
| Paint coverage | 350 ft² per gallon |
SOURCE — 1 acre = 43,560 ft², by definition.
SOURCE — 1 yd² = 3 ft × 3 ft = 9 ft², by definition.
SOURCE — one gallon covers ≈350 ft² on a smooth primed surface. Porous or textured surfaces take more.
Quick answers
A 12 ft × 10 ft room is 120 square feet. Square footage is always length × width in feet, and every other unit on this page is that number converted.
To subtract a door or window, work out its area the same way and take it off the total: a 3 ft × 7 ft door removes 21 ft² from the room.
120 square feet is 13.33 square yards. Divide square feet by 9, because a square yard is 3 ft × 3 ft.
One gallon of paint covers about 350 ft² on a smooth primed wall, so a 120 ft² wall takes roughly a third of a gallon per coat.
An acre is 43,560 square feet, which is why a 120 ft² room is 0.0028 acres — square footage and acreage are the same measurement at very different scales.
FAQ
How do I calculate the square footage of a room?
Measure the length and the width in feet and multiply them. A 12 ft × 10 ft room is 120 square feet. If the room is not a rectangle, split it into rectangles, work out each one, and add them together.
How do I work out square footage for flooring?
Use the floor area, then add for waste. Most flooring installers add 5–10% for cuts, and more for a diagonal or herringbone layout. For 120 ft² of floor at 10% waste you would order 132 ft².
How much does it cost per square foot?
Multiply your square footage by the price per square foot. At $4.50 per ft², a 120 ft² floor costs $540 in material before waste, delivery or labour.
How do I convert square feet to square metres?
Multiply square feet by 0.0929. A 120 ft² room is 11.15 m². The conversion is exact because an inch is exactly 25.4 mm by definition.
Do I subtract windows and doors from wall square footage?
For paint and drywall, yes — measure each opening and subtract it. For flooring there are no openings to subtract, though you should still take out anything permanent that sits on the floor, like a kitchen island.
How many square feet are in an acre?
43,560 square feet, by definition. A square acre is about 208.7 ft on each side, which is a useful check when you are pacing out a lot.