How to Measure a Room (Square Feet & Wall Area)
Floor area = length × width. Wall area = perimeter × ceiling height, minus doors and windows. Measure in feet, convert inches to decimals (6 in = 0.5 ft) and round up.
Measuring floor area
- Measure the longest wall-to-wall length and the widest width, at floor level.
- Convert inches to decimal feet (divide by 12) — or use our calculators' separate feet and inch boxes.
- Multiply length × width. A 12 ft 6 in × 10 ft room is 12.5 × 10 = 125 sq ft.
- Include closets and spaces under appliances that will get the new floor.
L-shaped and odd rooms
Sketch the room and split it into rectangles that don't overlap. Measure and calculate each, then add them. For an angled wall, treat that part as a triangle (base × height ÷ 2). Bay windows and curves can be approximated with a rectangle plus a half-circle.
Measuring wall area (paint, wallpaper, drywall)
Wall area = 2 × (Length + Width) × Ceiling height − openings
Door ≈ 21 sq ft (3 × 7 ft) · Window ≈ 15 sq ft (3 × 5 ft)
| Room | Floor area | Wall area (8 ft, 1 door, 2 windows) |
|---|---|---|
| 10×10 | 100 sq ft | 269 sq ft |
| 12×12 | 144 sq ft | 333 sq ft |
| 12×16 | 192 sq ft | 397 sq ft |
| 15×20 | 300 sq ft | 509 sq ft |
Tips
- Measure twice, at two points along each wall; rooms are rarely perfectly square.
- A laser measure is faster and more accurate than a tape for long rooms.
- Write measurements on your sketch so you can reuse them for paint, flooring and trim.
Then use the square footage calculator, flooring calculator or paint calculator.