How to calculate square feet
Measurements in inches: Length × Width ÷ 144 = square feet.
Measurements in feet: Length × Width = square feet.
For example, a 10 ft × 12 ft room has an area of 120 sq ft. If measurements are 77 inches × 33 inches, divide the product by 144 to convert the result to square feet.
Where a square feet calculator is useful
Use this calculator for room measurements, flooring estimates, ceiling areas, walls, furniture panels, plywood work, carpentry and basic construction planning. Keeping the measurement unit consistent helps avoid calculation errors.
Square feet vs square inches
One square foot contains 144 square inches. That is why measurements given in inches use the ÷ 144 formula. When both dimensions are already in feet, simply multiply length by width.
Worked examples you can check
Room measured in feet: 10 ft × 12 ft = 120 sq ft. This is the floor area before allowing for cupboards, cut-outs or material wastage.
Small panel measured in inches: 77 in × 33 in = 2,541 sq in. Divide 2,541 by 144 to get about 17.65 sq ft.
Metric measurements: a 3 m × 4 m room has an area of 12 sq m, or approximately 129.17 sq ft. Convert both dimensions to the same unit before multiplying; this calculator currently accepts feet or inches only.
Measuring an L-shaped room
Divide an L-shaped floor into two non-overlapping rectangles. Measure the length and width of each rectangle, calculate each area separately, and add the two results. Do not count the shared corner twice. For a wall or floor with permanent openings, subtract those areas only when the estimate calls for net usable surface.
Common area-measurement mistakes
- Multiplying feet by inches without converting one of the units first.
- Confusing a linear foot with a square foot: area requires two dimensions.
- Using rounded measurements for a material order without checking the actual site dimensions.
Useful conversions: 1 square yard = 9 sq ft; 1 square metre is approximately 10.7639 sq ft. Record the original unit with the result so measurements can be checked later.
Related PenniTools calculators
For related construction work, try the Tile Calculator for tile quantities, the Paint Calculator for paint estimates, and the Concrete Calculator for concrete volume.