Square Footage Calculator
Convert any area into square feet, square yards, square metres and acres.
How this calculator works
square feet = length × width × quantity
For a triangle, use half the base times the height. For a circle, use 3.1416 times the radius squared. Any irregular space can be broken into these three shapes and totalled.
Switch the site to metric — the control is in the footer — and your inputs, your results and the tables below follow. The formula, the constants, the guidance text and the sources stay in US units on purpose: that is how the standards they come from are written, and restating them would detach each figure from the document you are meant to be able to check it against.
Where these numbers come from
This one asserts nothing. Area is length times width — there is no constant here that a standard could fix, and citing one would only borrow authority the arithmetic does not need.
Worked example
With length 20 ft, width 15 ft, number of identical areas 1 , this calculator returns 300 sq ft.
Square feet by room width
Figures below assume length 12 ft × number of identical areas 1 . Open any row to load it into the calculator above — the link carries the numbers with it, so it can go straight to a supplier or a crew.
| Width | Area (sq ft) | Square metres |
|---|---|---|
| 8 ft | 96.00 | 8.92 |
| 10 ft | 120.0 | 11.15 |
| 12 ft | 144.0 | 13.38 |
| 14 ft | 168.0 | 15.61 |
| 16 ft | 192.0 | 17.84 |
| 20 ft | 240.0 | 22.30 |
For a 12 ft long room. Multiply by your own length in twelfths — a 24 ft long room is double these figures.
Square footage of common rooms and spaces
Open any row to load it into the calculator above — the link carries the numbers with it, so it can go straight to a supplier or a crew.
| Job | Size | Area |
|---|---|---|
| Bathroom | 8 ft × 6 ft × 1 | 48.00 sq ft |
| Bedroom | 12 ft × 11 ft × 1 | 132.0 sq ft |
| Living room | 18 ft × 14 ft × 1 | 252.0 sq ft |
| Two-car garage | 24 ft × 24 ft × 1 | 576.0 sq ft |
| Single-storey house footprint | 50 ft × 28 ft × 1 | 1,400 sq ft |
| Quarter-acre lot | 110 ft × 99 ft × 1 | 10,890 sq ft |
| Standard shipping container | 20 ft × 8 ft × 1 | 160.0 sq ft |
| Tennis court | 78 ft × 36 ft × 1 | 2,808 sq ft |
| Four identical offices | 12 ft × 10 ft × 4 | 480.0 sq ft |
For rooms that are not rectangular, split the space into rectangles, work out each one and add them together. Use the quantity field to repeat an identical space.
Square foot conversions
| Type | Square feet | Notes |
|---|---|---|
| 1 square yard | 9.00 | Carpet and some flooring is sold this way |
| 1 square metre | 10.76 | The metric equivalent |
| 1 square (roofing) | 100.0 | The unit roofers order in |
| 1 board (drywall, 4×8) | 32.00 | Standard sheet coverage |
| 1 acre | 43,560 | A square acre is about 209 ft on each side |
| 1 square (roofing/siding) | 100.0 | The unit both trades order in |
| 1 sheet of plywood (4×8) | 32.00 | Useful for estimating subfloor |
| 1 hectare | 107,639 | 2.47 acres |
To go the other way, divide: 500 square feet is 500 ÷ 10.764 = 46.5 square metres.
Square footage questions
How do I calculate square footage?
Multiply length by width, both in feet. A room 20 ft by 15 ft is 300 square feet. For an irregular space, divide it into rectangles, calculate each and add them together.
How many square feet are in a square yard?
Nine, since a yard is three feet and area scales with the square. Carpet and some flooring are still sold by the square yard, so divide your square footage by nine.
How do I find the area of a circle or triangle?
A circle is 3.1416 times the radius squared. A triangle is half the base times the perpendicular height. Both give square feet directly when you measure in feet.
How do I convert square feet to square metres?
Divide by 10.764. A 1,500 sq ft house is 139.4 square metres. To go the other way, multiply square metres by 10.764.
How do you calculate square footage of a house?
Measure each floor externally and add them, excluding the garage, unfinished basement and attic. Listed square footage normally means finished, heated living space — which is why the figure on a listing rarely matches a tape measure.
How much extra should I order for flooring?
Ten percent for straight-laid plank or tile, 15% for diagonal or herringbone patterns, and 20% for a room with many angles. Order from the same batch — dye lots vary noticeably between production runs.
How do I work out an irregular shape?
Break it into rectangles and triangles. A triangle is half its base times its height. Add the pieces together, and use the quantity field above to repeat any identical section.
How many square feet is a 10x10 room?
One hundred. It is also exactly one roofing square, which is why 10x10 is the reference people reach for when estimating anything sold by the square.
Does square footage include the garage?
No. Listed square footage means finished, heated living space. Garages, unfinished basements, attics and covered porches are all excluded, which is why a listing figure rarely matches a tape measure.
How do I measure a room with a bay window?
Treat the bay as a separate rectangle or trapezoid and add it. For a trapezoid, average the two parallel sides and multiply by the depth.
How many square feet are in an acre?
Exactly 43,560. A square acre measures roughly 209 ft on each side, which is a useful reference when pacing out land.