Free Contractor Tool
Square Footage Calculator
Measure any room, wall, or lot — rectangles, L-shapes, triangles, circles, and trapezoids. Add as many areas as you need, mix feet, inches and metres, and get the total square footage plus the material you'll actually have to buy once waste is included.
Length × Width
Total area
0
square feet
- Square metres
- 0
- Square yards
- 0
- Square inches
- 0
Material to order
How to calculate square feet
Square footage is area expressed in square feet. For any rectangular space you measure the length and the width in feet and multiply them together:
A room that is 12 feet long and 10 feet wide is 12 × 10 = 120 square feet. Everything else — odd shapes, mixed units, whole houses — is a variation on that one formula.
If you measured in inches
Divide each measurement by 12 before multiplying. Six inches becomes 0.5 feet; a wall measured at 138 inches is 11.5 feet. If you would rather multiply first, divide the result by 144 instead — there are 144 square inches in a square foot (12 × 12), which is why that number shows up so often.
Irregular and L-shaped rooms
Break the space into rectangles, work out each one, then add them together. The L-shape option above does this for you: enter the overall bounding box, then the notch that is missing from the corner, and it subtracts one from the other.
Walls, not floors
For paint or drywall, multiply wall width by ceiling height, then subtract the openings. A 12 ft × 8 ft wall is 96 ft²; take off two 3 × 4 windows (24 ft²) and you are painting 72 ft². Add each wall together for the room total.
Whole houses
Measure each finished room separately and add the totals. Note that appraisers following the ANSI standard measure from the exterior walls and exclude unfinished basements and garages, so a listing's square footage will not always match the sum of the rooms you walk through.
Why waste factor matters
Never order exactly the measured area. Cuts, pattern matching and breakage mean you need more material than the floor covers. Ten percent is the common default for straightforward tile and flooring; go to 15% for diagonal or herringbone layouts, and higher for large-format tile or patterned material where offcuts are unusable. Getting this wrong is one of the most common ways a job goes over budget on materials.
Common room sizes
| Dimensions (ft) | Square feet | Square metres |
|---|---|---|
| 8 × 10 | 80 | 7.4 |
| 10 × 10 | 100 | 9.3 |
| 10 × 12 | 120 | 11.1 |
| 12 × 12 | 144 | 13.4 |
| 12 × 16 | 192 | 17.8 |
| 14 × 20 | 280 | 26.0 |
| 20 × 20 | 400 | 37.2 |
| 24 × 24 | 576 | 53.5 |
| 30 × 40 | 1,200 | 111.5 |
| 40 × 60 | 2,400 | 223.0 |
Measuring is the easy part. Pricing it is not.
Kaliun turns takeoffs into priced, branded estimates — cost catalogs, markup rules, client selections and e-signatures — so the square footage you just worked out becomes a proposal instead of another spreadsheet.
See how estimating worksSquare footage questions, answered
- How do you calculate square feet?
- Measure the length and the width of the space in feet and multiply them together. A room 12 feet long and 10 feet wide is 12 × 10 = 120 square feet. If you measured in inches, divide each measurement by 12 first, or divide the final result by 144.
- How many square feet is a 12x12 room?
- A 12 by 12 foot room is 144 square feet (12 × 12 = 144). That is roughly 13.4 square metres.
- How many square feet is a 10x10 area?
- A 10 by 10 foot area is 100 square feet (10 × 10 = 100), about 9.3 square metres.
- How many square feet is 30x40?
- A 30 by 40 foot space is 1,200 square feet (30 × 40 = 1,200), around 111.5 square metres.
- Why do you divide by 144 to get square footage?
- Because there are 144 square inches in one square foot. A square foot is 12 inches by 12 inches, and 12 × 12 = 144. So if you multiply two measurements taken in inches, the result is in square inches — divide by 144 to convert it to square feet.
- How do you calculate the square footage of an irregular or L-shaped room?
- Break the space into rectangles, calculate each one, then add them together. For an L-shape you can also measure the full bounding rectangle and subtract the missing corner notch, which is what the L-shape option in the calculator above does.
- How do you calculate the square feet of a wall?
- Multiply the wall width by the ceiling height, then subtract the openings. A 12 ft by 8 ft wall is 96 square feet; deduct two 3 ft by 4 ft windows (24 square feet) and you have 72 square feet of paintable surface.
- How much extra material should I order for waste?
- Ten percent over the measured area is the usual default for straightforward tile and flooring. Use 15% for diagonal or herringbone layouts, and more for large-format or patterned material where offcuts cannot be reused.
- How do you convert square metres to square feet?
- Multiply square metres by 10.7639. One square metre is 10.7639 square feet, and one square foot is 0.0929 square metres. The calculator above converts automatically if you select metres as your measurement unit.