How to use the square footage calculator
Pick a shape and enter its sizes in feet. For a room that isn't a plain rectangle, split it into simple shapes and use Add another area for each one. To take something out, such as a kitchen island you won't floor under or a fireplace hearth, add it as a separate area and switch on Subtract this area.
Measurements in feet and inches need converting first: divide the inches by 12. 10 ft 6 in is 10.5 ft, and 10 ft 9 in is 10.75 ft.
Square footage formulas by shape
| Shape | Formula | Example |
|---|---|---|
| Rectangle or square | length × width | 12 × 14 = 168 sq ft |
| Triangle | base × height ÷ 2 | 10 × 6 ÷ 2 = 30 sq ft |
| Circle | π × (diameter ÷ 2)² | 12 ft across = 113.1 sq ft |
| Trapezoid | (side 1 + side 2) ÷ 2 × height | (8 + 5) ÷ 2 × 2 = 13 sq ft |
Worked example: an L-shaped living room
The main part of the room is 14 × 12 ft. A dining nook 8 ft wide sticks out 6 ft on one side.
- Main rectangle: 14 × 12 = 168 sq ft.
- Nook: 8 × 6 = 48 sq ft.
- Total: 168 + 48 = 216 sq ft, or 24 square yards.
Split along any line you like: the total is the same as long as the pieces don't overlap. Our L-shaped room guide shows both ways with a drawing.
With a cut-out: a 16 × 13 ft kitchen with a 6 × 3 ft island you won't tile under is 208 − 18 = 190 sq ft.
Common room sizes in square feet
| Room | Square feet | Square yards | Square meters |
|---|---|---|---|
| 10 × 10 ft | 100 | 11.11 | 9.29 |
| 10 × 12 ft | 120 | 13.33 | 11.15 |
| 12 × 12 ft | 144 | 16 | 13.38 |
| 12 × 14 ft | 168 | 18.67 | 15.61 |
| 14 × 16 ft | 224 | 24.89 | 20.81 |
| 15 × 20 ft | 300 | 33.33 | 27.87 |
| 20 × 20 ft | 400 | 44.44 | 37.16 |
| 24 × 24 ft | 576 | 64 | 53.51 |
Measuring tips that keep the number right
- Measure wall to wall at floor level, not along baseboards that might be thicker in places.
- Measure both ends of each wall. Old rooms are rarely square. Use the larger number when buying material.
- Include closets if the flooring goes into them; most flooring does.
- Round up to the next half foot for material estimates. Rounding down is how projects come up one box short.
- Sketch the room and write each measurement on the drawing. It makes the split into rectangles obvious.
Questions people ask
How do I calculate square feet from inches?
Multiply length by width in inches, then divide by 144 (12 × 12). A 48 × 30 in rug is 1,440 ÷ 144 = 10 sq ft.
How do I convert square feet to square yards?
Divide by 9, because a square yard is 3 ft × 3 ft. 180 sq ft is 20 square yards. Carpet is still often priced by the square yard.
Is square footage the same as linear feet?
No. Linear feet measure length only, like baseboard or a board. Square feet measure a surface. You need both: square feet for the floor, linear feet for the trim around it.
Does a home's listed square footage include the walls?
Listings and appraisals usually measure from the outside of exterior walls, so the listed figure is larger than the sum of the rooms measured inside. For buying material, always measure the room itself.