Square Footage Calculator with Feet and Inches
This square footage calculator feet and inches tool takes a length and a width exactly as your tape reads them, feet in one box and inches in the next. It returns the area in square feet, plus square inches and square meters; if your measurements are already metric, use the square meter calculator.
How to calculate square footage with feet and inches
Divide the inches by 12, add them to the feet, then multiply length by width. There are exactly 12 inches in a foot, per the NIST conversion factors (1 ft = 0.3048 m and 1 in = 0.0254 m, both exact).
Square feet = (feet + inches ÷ 12) × (feet + inches ÷ 12)
- Measure both walls at floor level and write down feet and inches separately.
- Turn each reading into decimal feet: inches ÷ 12, added to the whole feet.
- Multiply length by width to get square feet.
- Round only the answer, never the walls. Rounding 12 ft 6 in up to 13 ft adds a whole 6 inch strip of floor.
Example: a hallway of 22 ft 9 in by 3 ft 6 in is 22.75 × 3.5 = 79.625, which the calculator shows as 79.63 square feet (11,466 square inches).
Why 6 inches is 0.5 feet, not 0.6
Inches are twelfths of a foot, not tenths, so 12 ft 6 in is 12.5 ft. Writing 12.6 means six tenths of a foot, which is 7.2 inches.
On the room drawn above, that mistake adds 1.66 square feet.
Square feet, with 6 in read as 0.6 and 3 in as 0.3.
Square feet, with each inch counted as 1/12 of a foot.
Inches to decimal feet
Only 3, 6 and 9 inches give tidy decimals: 0.25, 0.5 and 0.75 feet. The rest (1, 2, 4, 5, 7, 8, 10 and 11 in) give repeating decimals, which is why the calculator keeps full precision and rounds only the result.
Inches to decimal feet chart, 1 to 12 inches
| Inches | Fraction of a foot | Decimal feet |
|---|---|---|
| 1 | 1/12 | 0.083 |
| 2 | 1/6 | 0.167 |
| 3 | 1/4 | 0.25 |
| 4 | 1/3 | 0.333 |
| 5 | 5/12 | 0.417 |
| 6 | 1/2 | 0.5 |
| 7 | 7/12 | 0.583 |
| 8 | 2/3 | 0.667 |
| 9 | 3/4 | 0.75 |
| 10 | 5/6 | 0.833 |
| 11 | 11/12 | 0.917 |
| 12 | 1 | 1 |
For an area that's already in square inches, divide by 144 instead (12 × 12) with the square inches to square feet converter.
Fractions of an inch
Type a fraction into the inches box as a decimal: 10 3/8 in goes in as 10.375. The box takes decimals but not a slash, and it accepts more than 12 inches, so a reading taken all in inches (150 in) works with 0 in the feet box.
| Tape reading | Decimal inch |
|---|---|
| 1/8 | 0.125 |
| 1/4 | 0.25 |
| 3/8 | 0.375 |
| 1/2 | 0.5 |
| 5/8 | 0.625 |
| 3/4 | 0.75 |
| 7/8 | 0.875 |
An eighth of an inch is about 0.01 ft, so it barely moves a room total. It matters on countertops, stair treads and tile cuts.
Square feet back to feet and inches
You can't turn an area into one length, but you can get a missing side. Divide the square footage by the side you know, then multiply the decimal part by 12 for the inches.
128.125 sq ft ÷ 12.5 ft = 10.25 ft. Then 0.25 × 12 = 3 in, so the other wall is 10 ft 3 in.
Take the square root: 150 sq ft is 12.247 ft a side, and 0.247 × 12 is about 3 in, so roughly 12 ft 3 in square.
This calculator handles one rectangle. For several rooms or an L-shape, the room calculator adds areas in feet and inches; the how to calculate square footage guide covers closets and bump-outs, and the main square footage calculator does circles and triangles.
Frequently asked questions
How do I calculate square footage with feet and inches?
Convert each measurement to decimal feet by dividing the inches by 12 and adding the whole feet, then multiply length by width. A 15 ft 6 in by 13 ft room is 15.5 × 13 = 201.5 square feet.
Is 12 feet 6 inches 12.6 or 12.5 feet?
It's 12.5 feet, because 6 inches is half of a 12 inch foot. 12.6 feet is 12 ft 7.2 in.
How do I convert inches to decimal feet?
Divide the inches by 12. For example, 4 inches is 4 ÷ 12 = 0.333 feet and 8 inches is 0.667 feet.
How do I enter 8 and 5/8 inches in the calculator?
Divide the top of the fraction by the bottom (5 ÷ 8 = 0.625) and type 8.625 in the inches box. The calculator then divides by 12 for you.
How do I convert square feet to feet and inches?
Divide the area by the side you know to get the other side in decimal feet, then multiply the decimal part by 12 for the inches. A 150 square foot room with a 12 foot wall has 150 ÷ 12 = 12.5 feet on the other side, which is 12 ft 6 in.