How to use the square footage calculator
Each box above is one area. Choose its shape, enter the measurements and pick the unit you measured in. Click Add another area for each extra room, bed or section, and tick Subtract this for anything you want taken out, like a kitchen island in a flooring job or a pond in a lawn. The total updates as you type, and the link button saves every area in the address so you can come back to it.
Formulas for each shape
| Shape | Area |
|---|---|
| Rectangle or square | length × width |
| Circle | π × (diameter ÷ 2)² |
| Triangle | base × height ÷ 2 (height measured square to the base) |
| Trapezoid | (side a + side b) ÷ 2 × height (a and b are the two parallel sides) |
Convert every measurement to feet before multiplying. 6 inches is 0.5 ft, not 0.6. If you measured in inches throughout, multiply in inches and divide by 144 at the end.
Worked example: two rooms
A living room of 12 × 14 ft and a dining room of 10 × 8 ft:
- Living room: 12 × 14 = 168 ft².
- Dining room: 10 × 8 = 80 ft².
- Total: 168 + 80 = 248 ft², which is about 23 m² or 27.6 yd².
For flooring you'd add 5 to 10% for cuts, so buy about 265 to 275 ft² of material.
How to measure a room or yard
- Measure wall to wall at floor level, ignoring baseboards. Round up to the next inch.
- Split L-shapes and odd rooms into rectangles. Draw a quick sketch, number each rectangle, and enter each one as its own area.
- Include closets if the flooring runs into them. Leave out areas under fixed cabinets.
- For yards, a 100 ft tape or a measuring wheel is easier than pacing. For a large or irregular lot, the acreage calculator handles four-sided plots with unequal sides.
- Bay windows and curves: a semicircle is half a circle, so enter it as a circle and halve the result, or treat a shallow bay as a trapezoid.
Square footage of a house
Real estate square footage follows different rules from a flooring estimate. In the US, the ANSI Z765 standard measures finished, heated living space from the exterior walls and leaves out garages and unfinished basements. Appraisers follow it; flooring installers measure inside each room. Neither is wrong, but don't compare one with the other.
Common mistakes
- Multiplying feet by inches. 12 ft × 6 in is 6 ft², not 72.
- Measuring a triangle's slanted side as its height. The height must be at right angles to the base.
- Forgetting doorways and alcoves where flooring continues. Small areas add up across a whole house.
Questions people ask
How do you calculate square footage?
Multiply length by width, with both in feet. A 12 × 14 ft room is 168 square feet. For an L-shaped or irregular space, split it into rectangles, work out each one, and add them together.
How do I measure square footage in inches?
Multiply length by width in inches and divide by 144, because a square foot is 12 × 12 = 144 square inches. Or pick inches in the unit box above and the calculator converts for you.
How many square feet is a 12x12 room?
144 square feet. A 10 × 10 room is 100, a 12 × 15 room is 180, and a 20 × 20 room is 400.
How do I find the square footage of a circle?
Square the radius (half the diameter) and multiply by 3.1416. A circle 10 ft across has a radius of 5 ft, so its area is 5 × 5 × 3.1416 = 78.5 square feet.
How do I convert square feet to square meters?
Multiply square feet by 0.0929. 248 ft² is about 23 m². To go the other way, multiply square meters by 10.764.
Should I add extra square footage for flooring?
Yes. Add 5 to 10% for straight lays of tile, laminate or vinyl plank, and 15% or more for diagonal or herringbone patterns, to cover cuts and breakage.
Sources and assumptions
- NIST Handbook 44, Appendix C: 1 ft² = 0.09290304 m²; 1 yd² = 9 ft²; 1 acre = 43,560 ft²
- Area formulas: rectangle l × w, circle πr², triangle ½ × base × height, trapezoid ½ × (a + b) × height.
Last reviewed 26 October 2026. Every formula on this page is checked against the worked example above in our automated tests. Found a problem? Tell us.