How to calculate square footage
- Measure the length and width of the space with a tape, to the nearest inch.
- Turn inches into feet by dividing by 12, so 6 inches is 0.5 feet.
- Multiply the length in feet by the width in feet to get square feet.
- For an odd shape, split it into rectangles, circles or triangles, find each area, add them, and subtract any cut-outs.
- If you are buying material, add about 10 percent for cuts and waste.
Buying flooring? Add the waste and count the boxes in the flooring calculator.
Square footage formulas by shape
Every shape starts with lengths in feet. The calculator turns inches, yards, meters and centimeters into feet first, then applies the formula, so you can type whatever your tape measure shows.
| Shape | Formula | Example |
|---|---|---|
| Rectangle | length x width | 12 ft x 12 ft = 144 sq ft |
| L-shape (two or more rectangles) | area of A + area of B | A 240 sq ft + B 80 sq ft = 320 sq ft |
| Circle | pi x radius x radius | pi x 5 ft x 5 ft = 78.54 sq ft |
| Triangle | 0.5 x base x height | 0.5 x 10 ft x 6 ft = 30 sq ft |
For a triangle with three known sides, the calculator uses Heron's formula: with s as half the total of the sides, the area is the square root of s x (s - a) x (s - b) x (s - c).
Common room sizes in square feet
Typical room sizes, worked out with the same math as the calculator.
| Room size (ft) | Square feet | Square yards | Square meters |
|---|---|---|---|
| 10 x 10 | 100 | 11.11 | 9.29 |
| 10 x 12 | 120 | 13.33 | 11.15 |
| 12 x 12 | 144 | 16 | 13.38 |
| 12 x 14 | 168 | 18.67 | 15.61 |
| 12 x 16 | 192 | 21.33 | 17.84 |
| 14 x 16 | 224 | 24.89 | 20.81 |
| 15 x 20 | 300 | 33.33 | 27.87 |
| 20 x 20 | 400 | 44.44 | 37.16 |
| 24 x 24 | 576 | 64 | 53.51 |
| 30 x 40 | 1,200 | 133.33 | 111.48 |
Square feet in other units
- 1 sq ft = 144 sq in. Convert with square inches to square feet.
- 9 sq ft = 1 sq yd. See square yards and carpet.
- 1 sq ft = 0.0929 m². Use square feet to square meters.
- 43,560 sq ft = 1 acre. Use square feet to acres.
About this area calculator
This tool works like a square feet calculator: pick a shape, type your measurements and read the result in square feet, square yards, square meters, square inches and acres. Think of it as a sq ft calculator that shows its working, so you can check every number. It does not use maps or satellite images, and it does not work out volume or depth.
Frequently asked questions
How do you calculate square footage?
Multiply the length by the width, with both measured in feet. A room 12 feet long and 10 feet wide is 12 x 10 = 120 square feet. For an odd shape, split it into rectangles, work out each one, and add them together. Measure to the nearest inch and turn inches into feet by dividing by 12.
How many square feet is a 12x12 room?
A 12 by 12 foot room is 144 square feet, because 12 x 12 = 144. That is 16 square yards or about 13.38 square meters. If you are buying flooring for it, add about 10 percent for cuts and waste, which brings the amount to buy to about 158.4 square feet.
How do you find the square footage of a circle?
Multiply pi, about 3.1416, by the radius squared. The radius is half the diameter, so a round area 10 feet across has a radius of 5 feet and an area of 3.1416 x 5 x 5, about 78.54 square feet. Choose Circle in the calculator above and enter either the radius or the diameter.
How do you find the square footage of an L-shaped room?
Split the L into two rectangles, find the area of each, and add them. For example, a 20 by 12 foot section plus a 10 by 8 foot section is 240 + 80 = 320 square feet. Choose L-shape in the calculator above, enter each part, and add more sections for rooms with extra corners.
How do you calculate square feet with feet and inches?
Turn the inches into part of a foot by dividing by 12, then multiply. A wall 12 feet 6 inches long is 12.5 feet, so 12 feet 6 inches by 10 feet is 12.5 x 10 = 125 square feet. The calculator above has a separate inches box, so you can type tape measure readings directly.
How do you calculate cost per square foot?
Multiply the area by the price per square foot to get the total, or divide a total price by the area to get the price per square foot. At $3.50 per square foot, 1,200 square feet costs 1,200 x 3.50 = $4,200. Enter a price in the optional field above to see the total.