Square Footage Calculator
Add a row for each room or section, pick its shape, and enter the dimensions. Square feet, square yards, and square meters update as you type.
| Shape | Length / diameter (ft) | Width / height (ft) | Sq ft |
|---|
Circle uses diameter, not radius. The second field is ignored for circles.
How to calculate square footage
The formula depends on the shape of the space. Measure in feet and the result comes out in square feet directly.
For a whole floor plan, break it into shapes like this, find the area of each one, and add the areas together. That's what the calculator above does across rows.
Common room sizes
| Room size | Square footage |
|---|---|
| 8′ × 10′ | 80 sq ft |
| 10′ × 10′ | 100 sq ft |
| 10′ × 12′ | 120 sq ft |
| 12′ × 12′ | 144 sq ft |
| 12′ × 14′ | 168 sq ft |
| 14′ × 16′ | 224 sq ft |
| 15′ × 20′ | 300 sq ft |
| 20′ × 20′ | 400 sq ft |
Measuring an irregular room
Most rooms aren't a clean rectangle. Split the floor plan into pieces you can measure with a tape: a main rectangle plus a closet nook, or a rectangle plus a triangular bay window. Measure each piece, calculate its area with the matching formula above, then add every piece into one total. A bay window alcove that's 3′ wide and juts out 2′ adds a triangle of 3 × 2 ÷ 2 = 3 sq ft to the room's rectangle. Add a row per piece in the calculator and the running total handles the rest.
Square feet, square yards, and square meters
Flooring is often priced per square yard, and international specs use square meters. An acre is 43,560 square feet.
| Convert | Do this |
|---|---|
| Square feet to square yards | ÷ 9 |
| Square feet to square meters | × 0.0929 |
| Square yards to square feet | × 9 |
| Square meters to square feet | × 10.764 |
| Square feet to acres | ÷ 43,560 |
| Acres to square feet | × 43,560 |
Need to go the other direction and turn an area into a count of boards or planks? The linear foot calculator converts square feet to linear feet once you know the material's width.
Frequently asked questions
How many square feet is a 12x12 room?
12 × 12 = 144 square feet. That's a common bedroom size and a useful number to memorize for quick sanity checks.
How do I convert square feet to square yards?
Divide by 9. A 300-square-foot room is 300 ÷ 9 = 33.3 square yards, which matters when carpet or flooring is priced per yard.
Do closets count in a home's total square footage?
Under ANSI Z765, the standard most residential listings follow, square footage counts finished, heated, enclosed living area. Closets and hallways inside that finished area count. Garages, unheated porches, and unfinished basements don't, no matter what's stored inside them.
How do I measure the square footage of an irregular room?
Split it into rectangles, triangles, or circles you can measure on their own, find each area, and add them up. See the irregular-room section above for a worked example.
How many square feet is a 15x20 room?
15 × 20 = 300 square feet, about the size of a small garage or a two-car driveway.