How to use the square footage calculator
- Choose your unit. Measure in feet, inches, yards, meters or centimeters. The result is always shown in square feet plus the metric equivalent.
- Pick a shape and enter its dimensions. Most rooms are rectangles. Use triangle, circle or trapezoid for bay windows, round patios or angled walls.
- Add more areas. For an L-shaped room or a whole floor, split the space into simple shapes and add each one. The calculator adds them up.
- Add waste and price (optional). A waste allowance covers cuts and breakage. Enter the price per square foot to estimate the total cost.
Square footage formulas
Square footage is simply area measured in square feet. Convert every measurement to feet first, then use the formula for the shape:
Triangle: base × height ÷ 2
Circle: π × (diameter ÷ 2)²
Trapezoid: (a + b) ÷ 2 × height
To convert inches to feet, divide by 12. To convert square feet to square meters, multiply by 0.0929. One square yard is 9 square feet, and one acre is 43,560 square feet.
Worked examples
A bedroom
A bedroom measures 12 ft by 10 ft 6 in. Convert 6 inches to 0.5 ft, so the room is 12 × 10.5 = 126 sq ft. If you are buying laminate flooring with 10% waste, order about 126 × 1.10 = 138.6, so round up to 139 sq ft.
An L-shaped living room
Split the L into two rectangles: 20 ft × 14 ft = 280 sq ft, and 10 ft × 8 ft = 80 sq ft. The total is 360 sq ft. Add both as separate areas in the calculator and it will do the sum for you.
A round patio
A circular patio is 14 ft across. The radius is 7 ft, so the area is 3.1416 × 7 × 7 = 153.9 sq ft.
How much waste should I add?
| Material | Typical waste allowance |
|---|---|
| Carpet, vinyl sheet | 5% to 10% |
| Laminate and hardwood (straight lay) | 7% to 10% |
| Tile (straight pattern) | 10% |
| Tile or wood (diagonal or herringbone) | 15% to 20% |
| Sod | 5% to 10% |
Rooms with many corners, closets or doorways need the higher end of the range because there are more cuts.
Measuring tips for accurate results
- Measure wall to wall at floor level, not along the baseboard top.
- Round each measurement up to the nearest inch. A slightly larger estimate is cheaper than a second order.
- Include closets if the flooring continues into them. Skip areas under fixed cabinets or tubs.
- For home size, real estate listings usually count finished, heated living space only. Garages, unfinished basements and porches are listed separately.
Common uses
Square footage is the starting point for almost every home project: flooring, carpet and tile orders, sod and seed for lawns, roofing (in combination with pitch), heating and cooling sizing, painting ceilings, and comparing the price per square foot of homes for sale or rent. Once you know the area, use our concrete, gravel or mulch calculators to turn it into a volume you can order.
Frequently asked questions
How do I calculate square footage of a room?
Measure the length and width in feet and multiply them. A 12 ft by 15 ft room is 12 × 15 = 180 square feet. For irregular rooms, split the floor into rectangles, calculate each one and add them together.
How do I convert inches to square feet?
Multiply length by width in inches to get square inches, then divide by 144. For example, 60 in × 48 in = 2,880 sq in, which is 20 sq ft. Or convert each side to feet first by dividing by 12.
How many square feet are in a square meter?
One square meter equals about 10.764 square feet. One square foot equals 0.0929 square meters.
How do I find the square footage of an L-shaped room?
Divide the L into two rectangles, calculate the area of each, and add them. Add both rectangles as separate areas in the calculator above and it totals them automatically.
How many square feet are in an acre?
One acre is exactly 43,560 square feet, which is about 4,047 square meters.
Should I include closets when measuring for flooring?
Yes, if the new flooring will run into the closets. Measure each closet as its own rectangle and add it as a separate area.
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Last updated October 2026.