Square Footage Calculator
Work out square footage for rectangles, L-shaped rooms, triangles and circles, add rooms together, and convert to square yards, square meters and acres. Subtract an island or a stair opening, and add a waste allowance and a price per square foot for a material estimate.
Your numbers
Up to 8 areas, all in the same unit. Switch on “Subtract this area” for a stair opening, an island or anything you will not cover.
Optional. Extra for cuts and offcuts.
Optional. For a material cost.
Total square feet
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- Square yards
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- Square meters
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- Acres
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An estimate for quoting and ordering, not a substitute for measuring on site or for the installer's figures.
The calculation runs in your browser and ParrotNotes does not store your numbers. They sit in the page address so you can bookmark or share the result.
How to measure a room for square footage
Sketch the room and break it into rectangles. Most rooms are one rectangle, or two for an L; a bay window is often a small trapezoid, a gable end a triangle, a round patio a circle. Measure each piece wall to wall at floor level, in feet and inches, and round up to the next inch.
Then take out what you will not cover: a kitchen island, a fireplace hearth, a stair opening. Add a row for each and switch on "Subtract this area". Doing the same room twice with the same breakdown gives the same number, which is what you want when two people quote the same job.
Area formulas for each shape
Every shape comes down to one of five formulas, with all measurements in feet. For a triangle the height is measured at a right angle to the base; for a trapezoid, sides A and B are the two parallel sides and the height is the distance between them.
| Shape | Area | Example |
|---|---|---|
| Rectangle or square | length × width | 12 × 15 ft = 180 ft² |
| L-shape | two rectangles, added | 15 × 12 + 10 × 8 ft = 260 ft² |
| Triangle | base × height ÷ 2 | 10 × 6 ft ÷ 2 = 30 ft² |
| Circle | π × (diameter ÷ 2)² | 10 ft across = 78.54 ft² |
| Trapezoid | (side A + side B) ÷ 2 × height | (10 + 14) ÷ 2 × 5 ft = 60 ft² |
A worked example
A living room of 15 × 12 feet opens into a dining area of 10 × 8 feet: as an L-shape that is 180 + 80 = 260 square feet. A 6 × 3 foot kitchen island stays, so subtract 18: 242 square feet of floor. That is 242 ÷ 9 = 26.89 square yards, or 22.48 square meters.
With a 10% waste allowance you order 242 × 1.10 = 266.2 square feet, and at $4.50 a square foot the material comes to $1,197.90. Open "How it is calculated" under the result to see the same steps with your own numbers.
Waste: how much extra to order
Flooring, tile, sod and roofing all lose some material to cuts. A common rule of thumb is 5 to 10% extra on a plain room laid straight, and more for diagonal or patterned layouts, small rooms and rooms with many corners. It is a starting point, not a rule: the installer or the product's instructions have the figure for that material, and a few spare pieces from the same batch help with repairs later.
The price per square foot field works out the material cost on the area with waste. Labor, underlayment, trim and delivery are separate lines in most estimates.
Square feet to square yards, meters and acres
The factors are exact: a foot is 0.3048 meters, a square yard is 9 square feet and an acre is 43,560 square feet.
| Square feet | Square yards | Square meters | Acres |
|---|---|---|---|
| 100 | 11.11 | 9.29 | 0.0023 |
| 500 | 55.56 | 46.45 | 0.0115 |
| 1,000 | 111.11 | 92.9 | 0.023 |
| 2,000 | 222.22 | 185.81 | 0.0459 |
| 43,560 | 4,840 | 4,046.86 | 1 |
Floor area vs the square footage on a listing
The floor area you measure for flooring is not always the square footage on a home listing. In the US, appraisers for loans sold to Fannie Mae must measure single-family homes to the ANSI Z765-2021 standard, which reports finished above-grade area apart from below-grade area, so a finished basement or an unfinished room can make the two numbers differ. Use this calculator for material and quoting; for a listing or an appraisal, the measuring standard in your market decides.
Source, checked September 2026: Fannie Mae Selling Guide B4-1.3-05.
On the walkthrough
The measurements are the easy part to get right. What gets lost is everything said while you measure: the homeowner wants the hallway done too, the subfloor is soft by the back door, the budget is firm, the install has to finish before a date. Write it down room by room as you go, or record the walkthrough, and the estimate matches what the customer asked for.
More for reps who measure and quote: Building materials sales, Roofing sales training, HVAC sales training.
After the tape measure
The area goes in the estimate; what the homeowner said on the walkthrough goes in ParrotNotes: record the visit and get the summary and next steps.
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