How to calculate square footage
Square footage is the area of a flat surface measured in square feet. A square foot is a square 12 inches on each side, so a room 12 ft by 10 ft holds 120 of them. The calculator handles the shapes you meet in real rooms and yards and lets you combine them into one total.
Area formulas used
| Shape | Formula |
|---|---|
| Rectangle or square | length × width |
| Circle | π × (diameter ÷ 2)² |
| Triangle | base × height ÷ 2 |
| Trapezoid | (side a + side b) ÷ 2 × height |
| L-shape | overall length × overall width − missing corner |
Worked example: an L-shaped living room
A room measures 20 ft by 16 ft overall, but a 6 ft by 5 ft corner belongs to the hallway. The full rectangle is 320 sq ft and the missing corner is 30 sq ft, so the room is 290 sq ft. If you are laying laminate with 10% extra for cuts, buy 319 sq ft, which is 15 boxes of a product that covers 22 sq ft per box.
Measuring tips
- Measure wall to wall at floor level and round each measurement up to the next inch.
- Convert inches to decimal feet before multiplying: 10 ft 6 in is 10.5 ft, not 10.6 ft. Or simply select inches in the calculator.
- Subtract permanent obstacles you will not cover, such as a kitchen island or a fireplace hearth, using a section marked "subtract".
- Do not subtract closets if you plan to floor them too.
Going from area to materials
Square footage is the starting point for most material estimates. Multiply by the coverage of your product, or by a depth to get volume: a 300 sq ft slab 4 inches thick needs 100 cubic feet, about 3.7 cubic yards of concrete. Use the concrete calculator for slabs, the cubic yard calculator for soil and mulch, and the gravel calculator for stone, which also converts to tons.
Square footage for real estate
Listings usually report finished, heated living area. Measurement practices vary by market, so compare homes using the same standard, and ask whether a figure came from public records, an appraisal or the seller. Price per square foot is simply the price divided by the finished area, and the calculator's cost field works in reverse to estimate project budgets.
Frequently asked questions
How do you calculate square footage?
For a rectangle, multiply length by width in feet. For other shapes use their area formula, and for an irregular room split it into simple shapes and add the pieces together.
How many square feet are in a square meter?
One square meter equals about 10.764 square feet, and one square foot equals 0.0929 square meters.
How do I convert square inches to square feet?
Divide by 144, because a square foot is 12 inches by 12 inches.
How much extra flooring should I buy?
Plan on about 5–10% extra for straight-laid plank or tile in simple rooms, and 10–15% for diagonal or herringbone patterns, small rooms with many cuts, or patterned materials that must be matched.
Does house square footage include the garage?
No. Under the widely used ANSI Z765 measuring standard, garages, unfinished basements and open porches are reported separately from finished living area.
Sources and official references
- Characteristics of New Housing (floor area data) – U.S. Census Bureau
- Unit conversion: area units – National Institute of Standards and Technology (NIST)
Last reviewed October 10, 2026. Results are estimates for planning; see our disclaimer.
