Square Footage Calculator
Area in sq ft, sq yards, m² and acres
A 12 by 10 ft room is 120 square feet, which is 13.33 square yards or 11.15 square metres. Enter the dimensions of any room, wall, lot or garden in feet or metres and this square feet calculator gives the square footage of rectangles, circles and triangles, converted for flooring, paint, landscaping or a real-estate listing.
How to calculate square footage
For a rectangle, square footage is simply length × width, both measured in feet. Measure to the nearest inch and convert inches to a decimal by dividing by 12, so 12 ft 6 in becomes 12.5 ft.
Pick the shape above, enter the measurements, and set "number of areas" if you're adding up several identical rooms. Switch the units toggle to work in metres and the result still reports square feet alongside square metres.
Square footage is only step one on most jobs. The printable material coverage chart carries it through to volume and coverage, which is what you actually order in.
Square footage formulas by shape
Almost any real space is one of these, or a combination of two or three added together.
| Shape | Formula | Example |
|---|---|---|
| Rectangle or square | length × width | 12 × 10 = 120 ft² |
| Triangle | ½ × base × height | ½ × 12 × 8 = 48 ft² |
| Circle | π × radius² | π × 6² = 113 ft² |
| Trapezoid | ½ × (a + b) × height | ½ × (10+14) × 8 = 96 ft² |
| Ellipse | π × half-width × half-length | π × 4 × 6 = 75 ft² |
| L-shape or irregular | split into rectangles, then add | 120 + 48 = 168 ft² |
Once you have the square footage, the printable material coverage chart turns it into quantities: how far a yard of gravel, a bag of concrete, a box of tile or a gallon of paint goes across that area.
Square feet, yards, metres and acres
As an area calculator it converts as you go. The two conversions people look up most are square feet to square meters (or square feet to square metres, if you spell it the British way) and cubic feet to cubic yards, and mixing units is a classic source of expensive ordering errors. Carpet is quoted by the square yard, most of the world quotes square metres, and land is sold by the acre.
| Unit | In square feet | Typically used for |
|---|---|---|
| 1 square inch | 0.00694 ft² | Tile and trim detail |
| 1 square yard | 9 ft² | Carpet, some concrete |
| 1 square metre | 10.764 ft² | UK, Ireland, Europe, most of the world |
| 1 acre | 43,560 ft² | Land and lots |
| 1 hectare | 107,639 ft² (2.47 acres) | Land, metric countries |
| 1 square mile | 27,878,400 ft² (640 acres) | Large land parcels |
How to measure an L-shaped or irregular room
Split it. Draw the room roughly to scale, divide it into rectangles with straight pencil lines, measure each one, then add the results. Every irregular room becomes two or three simple rectangles.
Two things people get wrong. First, measure the full length of each rectangle, not the visible bit, so shared edges aren't double counted or missed. Second, for curved bays and alcoves, measure the largest rectangle that fits and add a triangle or half-circle for the rest. A slight overestimate is harmless; you were adding waste anyway.
For chimney breasts, kitchen islands and built-in cupboards, work out the main area first, then subtract those footprints. Use the "number of areas" field above to total several identical spaces at once.
Square footage for flooring and paint
Once you have the area, divide by the coverage of whatever you're buying and add roughly 10% for waste. Coverage figures for common materials:
| Material | Typical coverage | Work it out |
|---|---|---|
| Paint | 350 to 400 ft² per gallon | Paint calculator |
| Tile | Varies by tile size | Tile calculator |
| Laminate | About 20 ft² per box | Laminate calculator |
| Carpet | Sold by the yd² (9 ft²) | Carpet calculator |
| Sod | About 450 ft² per pallet | Sod calculator |
| Gravel at 2 in | About 104 ft² per ton | Gravel calculator |
| Mulch at 2 in | 162 ft² per yd³ | Mulch calculator |
| Concrete at 4 in | 81 ft² per yd³ | Slab calculator |
Common room sizes in square feet
Useful for sanity-checking a measurement or estimating before you have a tape in hand.
| Room | Typical size | Square footage |
|---|---|---|
| Small bedroom | 10 × 10 ft | 100 ft² |
| Standard bedroom | 12 × 12 ft | 144 ft² |
| Primary bedroom | 14 × 16 ft | 224 ft² |
| Bathroom | 5 × 8 ft | 40 ft² |
| Kitchen | 12 × 14 ft | 168 ft² |
| Living room | 15 × 20 ft | 300 ft² |
| Single garage | 12 × 22 ft | 264 ft² |
| Two-car garage | 20 × 20 ft | 400 ft² |
What counts as square footage in a house
For listings and appraisals, the figure quoted is gross living area: finished, heated and cooled space above grade. The widely used ANSI standard measures from the exterior walls of a detached home, which is why a listing figure is larger than the total of the rooms you measure inside.
Generally counted: finished rooms, hallways, and stairs (on each floor they serve). Generally not counted: garages, unfinished basements or attics, open porches, decks and balconies. Space needs roughly 7 ft of ceiling height to qualify.
Finished basements are usually reported separately as below-grade space rather than folded into the headline number, even when they are fully finished. Rules vary by region and lender, so for anything that affects a valuation, confirm with a local appraiser rather than relying on a calculator.
Square footage mistakes to avoid
- Mixing units. Convert inches to decimal feet before multiplying; 12 ft 6 in is 12.5, not 12.6.
- Using radius instead of diameter. A circle's formula needs the radius, which is half the width across.
- Forgetting to subtract. Islands, chimney breasts and built-ins reduce the floor you actually cover.
- Measuring walls as floors. For paint, measure wall height × perimeter, then subtract doors and windows.
- Ordering with no waste. Add about 10%, and more for diagonal or patterned layouts.
- Trusting a listing figure. It is measured externally and includes wall thickness, so it always exceeds usable floor area.
What the area figure assumes
Pure geometry, no material assumptions. Rectangles are length × width, circles πr², triangles ½ × base × height.
- Conversions are exact: 1 m² = 10.7639 ft², 1 yd² = 9 ft², 1 acre = 43,560 ft².
- The gross-living-area guidance reflects the ANSI measurement standard used by most US appraisers. Rules vary by region and lender, so confirm with a local appraiser for anything affecting a valuation.
Both unit systems. Metric mode takes metres and returns metric units throughout.
Sources, checked
- ANSI Z765 Square Footage Method: FAQ, Home Innovation Research Labs. Fannie Mae requires ANSI Z765-2021 of appraisers for gross living area.
Figures reviewed . Every worked example on this page is checked against the calculator above.
Square Footage Calculator: frequently asked questions
How do I calculate the square footage of a room?
Multiply the room's length by its width in feet. For an L-shaped room, split it into rectangles, find each area, and add them together. Convert inches to decimals first, so 12 ft 6 in becomes 12.5 ft.
How many square feet are in a square metre?
About 10.764 square feet. To convert square metres to square feet multiply by 10.764; to go the other way, divide by 10.764. Use the units toggle above to switch without converting by hand.
How many square feet are in an acre?
43,560 square feet, which is about 4,047 square metres. A hectare is 107,639 square feet, or roughly 2.47 acres. The calculator shows acreage automatically.
How do I measure square footage of an irregular room?
Break the space into rectangles and triangles, calculate each separately, then add them together. Subtract the footprint of islands, chimney breasts and built-in units, since you will not be covering those.
What counts as square footage in a house?
Finished, heated and cooled space above grade, measured from the exterior walls under the ANSI standard. Garages, unfinished basements and attics, open porches and decks are excluded, and space generally needs about 7 ft of ceiling height to count.
How many square feet is a 12x12 room?
144 square feet, which is 16 square yards or about 13.4 square metres. A 10x10 room is 100 square feet and a 14x16 room is 224 square feet.