Square Footage Calculator
Calculate square footage for rectangular, circular and triangular areas, with square meters, square yards and project cost.
How to calculate square footage
Square footage is the area of a space in square feet. Measure in feet and use the formula for the shape:
| Shape | Formula | Example |
|---|---|---|
| Rectangle | Length × Width | 15 × 12 = 180 ft² |
| Circle | π × (Diameter ÷ 2)² | 10 ft across = 78.5 ft² |
| Triangle | Base × Height ÷ 2 | 10 × 8 ÷ 2 = 40 ft² |
Irregular rooms
Split an L-shaped or irregular room into rectangles, calculate each, and add them together. For a bay window or alcove, measure it as its own rectangle or triangle. Do not subtract closets if you are buying flooring for them too.
Converting measurements
- Inches to feet: divide by 12. A room 12 ft 6 in long is 12.5 ft.
- Square feet to square meters: divide by 10.764.
- Square feet to square yards (used for carpet): divide by 9.
- One acre is 43,560 square feet.
Square footage of a house
Real estate listings in the US usually count finished, heated living space measured from exterior walls. Garages, unfinished basements and porches are normally excluded, and rules vary between appraisers and states, so a listing figure may differ from your own measurement of interior rooms.
Frequently asked questions
How do I calculate the square footage of a room?
Multiply the length by the width in feet. A 12 × 14 ft room is 168 square feet.
How many square feet is a 10 by 10 room?
100 square feet.
How do I convert square meters to square feet?
Multiply square meters by 10.764. For example, 20 m² is about 215 ft².
Last reviewed Oct 20, 2026. Results are estimates; check important decisions with a qualified professional.