Basic square-feet formula
If a room is 12 feet long and 10 feet wide, its area is 12 × 10 = 120 square feet.
When measurements are in inches
Convert inches to feet first, or calculate square inches and divide by 144.
For example, 77 × 33 inches = 2,541 square inches, which is 17.646 square feet.
Using centimetres or metres
For centimetres, convert each measurement to feet before multiplying, or convert the final square-centimetre result to square feet. For metres, one square metre is approximately 10.7639 square feet.
Rooms with multiple sections
Split an L-shaped or irregular room into rectangles, calculate each rectangle separately, then add the areas. Keep the same unit throughout the calculation to avoid conversion errors.
Why accurate area matters
Area is often the starting point for estimating tiles, paint, flooring and other materials. Material purchases may need extra allowance for cuts, breakage, overlaps or installation waste, depending on the project.
Use the Square Feet Calculator for quick area calculations. For flooring, continue to the Tile Calculator; for paint estimates, use the Paint Calculator.
Browse Construction Calculators for concrete, material and building estimates, or Carpenter Calculators for woodworking measurements.
Worked examples you can check
Room measured in feet
A room measuring 12 ft by 10 ft has an area of 12 × 10 = 120 sq ft. If a second rectangular section measures 4 ft by 3 ft, add 12 sq ft to get 132 sq ft total.
Measurements in feet and inches
Convert inches to decimal feet before multiplying. For example, 10 ft 6 in is 10.5 ft. A 10 ft 6 in by 8 ft room is 10.5 × 8 = 84 sq ft.
Square metres to square feet
Multiply square metres by 10.7639. A 20 m² floor is approximately 215.28 sq ft. Keep unrounded values during the calculation and round only the final result.
Estimating material quantities
Area is not always the same as the quantity to buy. Tiles need allowances for cuts and breakage; paint coverage depends on the product, surface texture and number of coats. Measure doorways, niches and irregular areas carefully, and follow the supplier's coverage guidance. For expensive work, verify measurements on site before ordering.
Common mistakes to avoid
- Multiplying measurements in different units without converting them first.
- Adding lengths instead of calculating each rectangular area's length × width.
- Forgetting to split L-shaped rooms into separate rectangles.
- Rounding each small section too early, which can create a larger total error.
Example for an Indian room renovation
Suppose a bedroom measures 12 ft 6 in by 10 ft 3 in. Convert the measurements first: 12 ft 6 in = 12.5 ft and 10 ft 3 in = 10.25 ft. The floor area is 12.5 × 10.25 = 128.125 sq ft, or about 128.13 sq ft.
If you are buying tiles, the order quantity is not simply 128.13 tiles. Divide the floor area by the coverage of one tile, then allow for cuts and breakage. If a tile covers 1 sq ft and you choose a 10% allowance, the estimate is ceil(128.125 × 1.10) = 142 tiles. Carton sizes and tile layout may change the purchase quantity, so confirm with the supplier.
On-site measurement checklist
- Measure each wall or floor section at least twice.
- Record feet and inches consistently, then convert to decimal feet before multiplying.
- Split L-shaped or irregular rooms into rectangles and add their areas.
- Decide whether openings should be subtracted based on the surface being measured.
- Keep the unrounded area for later material estimates; round the final purchase quantity up.
For a quick result, use the Square Feet Calculator. For tile quantities, use the Tile Calculator; the two results answer different questions.