What is square footage and why it matters
Square footage is the measure of a two-dimensional area expressed in square feet — the total number of one-foot-by-one-foot squares that fit inside a boundary. It is the single most useful number in home improvement, construction, interior design, and real estate, because it connects directly to how much material a project needs and how much a space is worth.
Whether you're laying flooring, painting walls, ordering tile, planning a garden bed, or comparing properties, getting the area right is the first step. This site gives you a dedicated calculator for every common shape, each with unit conversion across feet, yards, meters, inches, centimeters, miles and kilometers, plus an optional cost estimator so you can turn an area straight into a budget.
How to calculate square feet
For a rectangular room, measure the length and the width in feet and multiply them: square feet = length × width. A room 12 ft long and 14 ft wide is 12 × 14 = 168 sq ft.
Measurements in feet and inches: turn the inches into a decimal of a foot by dividing by 12, then multiply. A room 12 ft 6 in by 10 ft 3 in is 12.5 × 10.25 = 128.1 sq ft. In the calculators, enter 12.5 feet, or switch the box to inches and enter 150.
Odd-shaped rooms: split the floor into rectangles (and triangles or circles where needed), work out each area, then add them together. The L-shaped room calculator and combined-shapes guide walk through this.
Square footage of common room sizes
| Room size | Typical use | Square feet | Square yards | Square meters | Flooring to buy (+10%) |
|---|---|---|---|---|---|
| 10 × 10 ft | Small bedroom or home office | 100 | 11.1 | 9.3 | 110 |
| 10 × 12 ft | Standard bedroom | 120 | 13.3 | 11.1 | 132 |
| 12 × 12 ft | Large bedroom | 144 | 16.0 | 13.4 | 158 |
| 12 × 14 ft | Primary bedroom | 168 | 18.7 | 15.6 | 185 |
| 14 × 16 ft | Living room | 224 | 24.9 | 20.8 | 246 |
| 15 × 20 ft | Large living room or basement room | 300 | 33.3 | 27.9 | 330 |
| 20 × 20 ft | Two-car garage | 400 | 44.4 | 37.2 | 440 |
| 20 × 30 ft | Large garage or open-plan floor | 600 | 66.7 | 55.7 | 660 |
How to use these calculators
- Pick the shape that matches your space from the grid above.
- Enter your measurements and choose the unit for each — they don't all have to match.
- Add a price per unit (optional) to estimate total material cost.
- Press Calculate to see the area, and expand the unit table to view the result in every supported unit.
A quick tip: always add a waste factor
No real project uses the exact calculated area. For flooring and tile, add roughly 5–10% (more for diagonal patterns or irregular rooms) to cover cuts, mistakes, and damaged pieces. Buying slightly more is almost always cheaper than running out mid-job.