Square Footage Calculator
Measure square footage for rooms, flooring, painting, and more. Supports rectangular, triangular, and circular shapes. Useful for estimating materials and project costs.
Square footage is the bedrock measurement of home improvement, real estate, and construction. It tells you how much flooring to buy, how much paint to mix, how much sod to order, what you're paying per square foot of a home, and a hundred other things. The calculation is straightforward for rectangles — length times width — but rooms, yards, and walls are rarely perfect rectangles, and getting the math right requires breaking irregular shapes into simpler ones.
This calculator computes square footage for rectangular areas, and lets you multiply by a quantity (for repeated rooms) and price per square foot for cost estimates. For irregular layouts — L-shaped rooms, rooms with bay windows, yards with corners cut out — measure each rectangular section separately, calculate the square footage of each, and add them together.
Always measure twice. A 6-inch error in either dimension on a 200 sq ft room throws off material orders by about 10 sq ft, which can leave a flooring or carpet job short.
Inputs
Results
Total Square Footage
120 sq ft
Square Yards
13.3
Unit Conversions
| Unit | Value |
|---|---|
| Square Feet | 120 |
| Square Yards | 13.33 |
| Square Meters | 11.15 |
| Acres | 0.0028 |
Formula
How to use this calculator
- Measure the length and width of each rectangular section with a tape measure. Round to the nearest tenth of a foot (about an inch); precision below that rarely matters.
- Enter length and width in feet. For inches, convert: 1 inch = 0.0833 ft (or just enter "12.5" for 12 ft 6 in).
- If you have several rooms of the same size, use the "Number of Areas" field as a multiplier instead of running the calculator multiple times.
- For material cost estimation, enter price per square foot. Add 5–10% to total square footage to account for waste, cuts, and pattern matching on flooring/tile/carpet projects.
- For walls (paint), measure each wall as length × height and subtract doors and windows. A standard door is 21 sq ft; a typical window is 12–15 sq ft.
Worked examples
Carpet for a bedroom
Bedroom: 12 ft × 14 ft = 168 sq ft Most carpet is sold by the square yard: 168 / 9 = 18.67 sq yd Round up and add 10% for waste: 21 sq yd At $35/sq yd installed: $735 budget for the room.
Paint for a living room
Walls: two at 14 ft × 9 ft, two at 18 ft × 9 ft = (2 × 126) + (2 × 162) = 576 sq ft Subtract: 1 door (21 sq ft) + 3 windows (3 × 15 = 45 sq ft) = 66 sq ft Net wall area: 510 sq ft A gallon of paint covers about 350–400 sq ft, two coats. 510 sq ft × 2 coats = 1,020 sq ft of coverage. Need 3 gallons.
When to use this calculator
Use this any time you need to translate physical dimensions into a material order, a real estate listing, or a cost estimate. It's the right tool for floor plans, paint coverage, sod and lawn projects, room comparisons, and price-per-square-foot checks on home listings.
For very irregular shapes (circular features, sloped ceilings), use the dedicated geometry calculators on this site — circle, triangle, ellipse — to compute each section, then sum.
Real-estate listings in the U.S. typically use "gross living area" — finished interior space, excluding garages and unfinished basements. Be careful when comparing listings; "finished square footage" definitions vary by region and source.
Common mistakes to avoid
- Mixing inches and feet without converting. 12 ft 6 in is 12.5 ft, not 12.6 ft.
- Forgetting to subtract doors and windows when calculating wall paint area.
- Not adding waste factor on flooring and tile. 10% is standard; complex patterns or rooms with lots of cuts need 15–20%.
- Measuring once and trusting it. Tape measures slip; the room you measured at 14 ft might be 13 ft 9 in or 14 ft 2 in.
- Confusing square feet with linear feet on long-and-narrow features. A 10 ft × 6 in baseboard is 5 sq ft AND 10 linear feet; they're different specifications.
- Using exterior dimensions for interior square footage. Walls eat 4–6 inches per side; a house with 30 × 40 ft exterior footprint has less interior space.
Frequently Asked Questions
Sources & further reading
- Measuring square footage — Appraisal Institute