How to calculate square footage
Square footage is simply area measured in feet. To find it, multiply the length by the width of your space when both are measured in feet:
Square feet = Length (ft) × Width (ft)
A room that measures 12 feet by 10 feet has an area of 120 square feet. If you measured in another unit, this calculator converts it for you first — inches are divided by 12, yards multiplied by 3, and meters multiplied by 3.281 to get feet before the area is calculated.
Measuring different shapes
- Rectangle or square: length × width.
- L-shaped room: split into two rectangles, calculate each, then add them.
- Circle: π × radius² (radius is half the diameter).
- Triangle: ½ × base × height.
Estimating materials and cost
Once you know your square footage, multiply it by the price per square foot of your material to estimate cost. Always add a waste allowance — the field above defaults to 10%, which is a safe starting point for most flooring and tile jobs. Use 5% for simple straight-lay layouts and up to 15% for diagonal patterns or rooms with many corners.
For paint, remember coverage is roughly 350–400 square feet per gallon per coat, so a 120 sq ft wall needs less than a gallon for one coat but plan for two coats on new or dark surfaces.
Common conversions
- 1 square yard = 9 square feet
- 1 square meter ≈ 10.764 square feet
- 1 acre = 43,560 square feet
Frequently asked questions
How do you calculate square footage?
Multiply the length by the width, with both measurements in feet. For a room that is 12 ft by 10 ft, the area is 12 × 10 = 120 square feet. If your measurements are in inches, divide the result by 144 to convert to square feet.
How do I measure an irregular or L-shaped room?
Split the space into rectangles, calculate the square footage of each, then add them together. For circles, use π × radius². For triangles, use ½ × base × height.
How much extra material should I order?
For flooring and tile, add 5–10% for cuts and waste; 10% for diagonal or herringbone patterns. For paint, one gallon typically covers about 350–400 square feet per coat.
How many square feet are in a square yard or acre?
One square yard equals 9 square feet. One acre equals 43,560 square feet. This calculator shows the result in square feet; divide by 9 for square yards or by 43,560 for acres.
Disclaimer: Results are estimates for planning purposes. Always confirm measurements and material quantities before purchasing.