How to calculate square footage
Measure in feet, then use the formula for your shape. Convert inches first, so 6 in is 0.5 ft.
Rectangle = length × width
Circle = π × (diameter ÷ 2)²
Triangle = base × height ÷ 2
With waste = area × (1 + waste %)Worked example: a 15 × 12 ft room
- Area: 15 × 12 = 180 sq ft.
- If you're ordering flooring with 10% waste: 180 × 1.10 = 198 sq ft.
Measuring an L-shaped room
Split the room into rectangles that don't overlap, work out each one, then add them together. An L-shaped room made of a 12 × 10 ft section and an 8 × 6 ft section is 120 + 48 = 168 sq ft. To exclude a built-in feature such as a kitchen island, work out its area the same way and subtract it.
Measuring tips
- Measure at floor level along the longest straight runs, and check again at the other end of the room, since walls are rarely perfectly parallel.
- Round each measurement up to the nearest inch or so when you're ordering material. Small rounding is cheaper than a second trip.
- For a triangle, measure the height at a right angle to the base. A sloping side gives too large an answer.
Listing or insurance figures may differ
This gives the area of the space you measure. A home's official square footage can follow different rules about wall thickness, stairs and unfinished areas, so don't use this figure for a sale, appraisal or legal document.
Turn the area into a shopping list
Once you have the room size, the flooring calculator andtile calculator work out how many boxes to buy, and thepaint calculator does the same for walls.