How to use the square footage calculator
- Choose feet or meters. Every dimension uses the same unit.
- Pick the shape of the first area and enter its dimensions.
- To add another part, such as a closet or a bay window, pick a shape for Area 2. A new row appears each time, up to six areas.
- Optionally set the extra for waste you want to buy on top of the exact area.
- Optionally enter a price per square foot (or per m²) to see the cost.
How square footage is calculated
Each part of the floor is measured as a simple shape, and the areas are added together:
The height of a triangle or trapezoid is measured at a right angle to the base, not along a slanted side. For an L-shaped room, split it into two rectangles that don't overlap: measure the long leg along its full length, then the short leg from where it leaves the first rectangle. One square foot is 0.0929 m², and one square yard is 9 square feet.
Worked example
The default is a single rectangular room, 12 ft × 15 ft, with 10% extra for waste:
- Area: 12 × 15 = 180 sq ft
- In metric: 180 × 0.0929 = 16.72 m²; in square yards: 180 ÷ 9 = 20 sq yd
- Flooring to buy with 10% extra: 180 × 1.10 = 198 sq ft
Now add an L-shaped hallway as Area 2, made of a 10 × 8 ft part and a 6 × 4 ft part: 80 + 24 = 104 sq ft, so the total becomes 180 + 104 = 284 sq ft. If the 12 × 15 room were instead a trapezoid with a 12 ft top, a 15 ft bottom and a height of 6 ft, its area would be (12 + 15) ÷ 2 × 6 = 81 sq ft.
At $4.50 per sq ft, flooring for the original room costs 198 × $4.50 = $891.
Measuring tips
- Measure wall to wall at floor level, and round up to the next inch or centimeter.
- Measure each dimension twice. Older rooms are rarely square, so measure both lengths and use the larger.
- Leave out permanent fixtures such as kitchen islands only if the flooring won't run under them.
- Convert inches to decimal feet before entering them: 6 inches is 0.5 ft and 9 inches is 0.75 ft, so 12 ft 9 in is 12.75 ft.
- For a curved wall, a circle or part-circle is close enough for buying material; add a little extra waste.
How much extra to buy
| Material and layout | Typical extra |
|---|---|
| Carpet, sheet vinyl | 5–10% |
| Laminate or plank flooring, straight | 7–10% |
| Tile, straight layout | 10% |
| Tile or planks, diagonal or herringbone | 15–20% |
Extra covers cuts at walls and doorways, breakage and a few spare pieces for repairs later. For tile counts with grout lines and boxes, use the tile calculator.
Frequently asked questions
How do I calculate square footage of a room?
Multiply the length by the width in feet. A 12 ft by 15 ft room is 12 × 15 = 180 square feet. If the room isn't a rectangle, split it into rectangles and other simple shapes, work out each area and add them up.
How do I convert square feet to square meters?
Multiply square feet by 0.0929, or divide by 10.764. So 180 sq ft is about 16.72 m². To go the other way, multiply square meters by 10.764.
Do I measure the area of a room including closets?
Include closets and alcoves if the flooring or paint will go into them, and add them as separate areas so you can check each one. For listing a home's living area, the rules differ by region and usually exclude garages and unfinished spaces.
What is a square yard?
A square yard is 3 ft × 3 ft, or 9 square feet. Carpet is often priced per square yard, so divide your square footage by 9: a 180 sq ft room is 20 square yards.
Related calculators
- Tile Calculator — How many floor or wall tiles and boxes to buy, allowing for grout joints, layout waste and cost per box.
- Concrete Calculator — Concrete for slabs, footings, round columns, circular pads and steps, in cubic yards or m³, plus bags needed.
- Mulch Calculator — Cubic yards, cubic feet or m³ of mulch for a garden bed, plus how many 2 or 3 cu ft bags to buy.
- Area Calculator — Area of a square, rectangle, triangle, circle, ellipse, trapezoid, parallelogram, sector or regular polygon.
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