Square feet calculator for rooms, L-shapes and circles
Most rooms are rectangles: length × width = square feet. The calculator above handles the shapes that aren't.
- L-shaped room — split it into two rectangles that don't overlap, measure each, and add them. A 10 × 12 living room with a 6 × 8 dining nook is 120 + 48 = 168 sq ft.
- Circle — π × radius². A 10 ft round patio is 3.1416 × 5 × 5 = 78.5 sq ft.
- Triangle — base × height ÷ 2, where the height is measured square to the base. Gable-end walls and corner beds are triangles.
- Closets and hallways — switch on Add another rectangle so they land in the same total instead of being forgotten.
If you are measuring for flooring, measure every room at floor level from wall to wall and treat doorways between rooms as part of the bigger room. Baseboards and trim cover the last ¼–½ inch, so you never need to measure tighter than the nearest inch.
Square footage calculator with feet and inches
You can type measurements exactly as they come off the tape: 12' 6", 12 ft 6 in, 12 6 or 12.5. The calculator converts everything to decimal feet before multiplying, which is the step that trips most people up — 12 ft 6 in is 12.5 ft, not 12.6 ft.
| Inches | Decimal feet | Inches | Decimal feet |
|---|---|---|---|
| 1 in | 0.083 ft | 7 in | 0.583 ft |
| 2 in | 0.167 ft | 8 in | 0.667 ft |
| 3 in | 0.25 ft | 9 in | 0.75 ft |
| 4 in | 0.333 ft | 10 in | 0.833 ft |
| 5 in | 0.417 ft | 11 in | 0.917 ft |
| 6 in | 0.5 ft | 12 in | 1 ft |
Mixing them up costs real money at scale: a 14 ft 9 in × 11 ft 3 in bedroom is 165.9 sq ft, but reading the inches as decimals (14.9 × 11.3) gives 168.4 sq ft.
Square footage of common room sizes
| Room size | Square feet | Square yards | With 10% waste |
|---|---|---|---|
| 10 × 10 ft | 100 | 11.1 | 110 |
| 10 × 12 ft | 120 | 13.3 | 132 |
| 12 × 12 ft | 144 | 16 | 158 |
| 12 × 15 ft | 180 | 20 | 198 |
| 14 × 16 ft | 224 | 24.9 | 246 |
| 20 × 20 ft | 400 | 44.4 | 440 |
| 24 × 24 ft | 576 | 64 | 634 |
| 30 × 40 ft | 1,200 | 133.3 | 1,320 |
The waste column is what you should actually buy for click-lock flooring laid straight. Diagonal tile or herringbone patterns need 15% or more.
Mistakes that make square footage wrong
Using the listing's square footage for a flooring order. A home's advertised square footage is measured to the outside of exterior walls under the ANSI Z765 method, so it includes wall thickness and rooms you may not be covering. Measure the rooms you are actually doing.
Forgetting the closet. A reach-in closet is often 2 × 6 ft — 12 sq ft that comes out of your waste allowance if you forget it.
Buying the exact number. Flooring, tile and sod are cut to fit. Order the waste percentage on top, and buy flooring from one production lot so the color matches.
Once you have the number, take it straight into the flooring calculator for boxes, the tile calculator for tiles and thinset, or the paint calculator for gallons. For anything poured or spread — gravel, soil, concrete — multiply by depth with the cubic yard calculator.
