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Square Footage Calculator
Square feet of rooms and shapes in feet and inches, total area for several rooms and the cost per square foot.
Calculated in your browser – nothing you enter is sent or stored.
This square footage calculator works out the area of a room, floor, yard or lot in square feet. Enter measurements in feet and inches, choose a rectangle, circle or triangle, and add as many areas as you need – it totals them, converts to square yards, square meters and acres, adds a waste allowance and estimates the cost at a price per square foot.
How to Use the Square Footage Calculator
- Measure each area at its longest and widest points. Round up to the nearest inch.
- Choose the shape and enter the length and width (for a circle, the diameter; for a triangle, the base and height).
- For an L-shaped or irregular room, split it into rectangles and add each one with Add area.
- Enter a waste percentage and the price per square foot of your flooring, sod or paint job.
Square Footage Formulas
- Rectangle or square: length × width.
- Circle: π × radius², or π × (diameter ÷ 2)². A 10-ft circle is 78.5 sq ft.
- Triangle: base × height ÷ 2.
Convert inches to feet first by dividing by 12: 14 ft 6 in = 14.5 ft.
Example: a bedroom of 12 ft × 14 ft 6 in is 12 × 14.5 = 174 sq ft, and a 10 × 11 ft office is 110 sq ft – 284 sq ft in total. Adding 10% for cuts and waste means buying about 312 sq ft of flooring; at $4.50 per sq ft that is about $1,406.
Area Conversions
| Unit | In square feet |
|---|---|
| 1 square yard | 9 sq ft |
| 1 square meter | 10.764 sq ft |
| 1 acre | 43,560 sq ft |
| 1 square mile | 27,878,400 sq ft (640 acres) |
Carpet is often sold by the square yard: divide square feet by 9.
How Much Extra to Buy
- Hardwood, laminate and vinyl plank: 5%–10% for cuts.
- Tile: 10%, or 15% if laid on a diagonal or in a pattern.
- Sod: about 5%.
- Paint: measure wall area (perimeter × ceiling height) minus windows and doors; a gallon covers roughly 350–400 sq ft per coat.
Square Footage of a House
For real estate listings, "living area" usually counts finished, heated space measured from the outside walls, and excludes garages, unfinished basements and porches. The ANSI Z765 standard is widely used, but rules vary by state and appraiser. For a slab or patio, use the concrete calculator to turn the area into cubic yards.
Sources
- NIST – Unit conversion (area)
- Fannie Mae Selling Guide – gross living area and the ANSI Z765 measuring standard
Last reviewed: October 2026 by the ShrinkBee team. Results are estimates for planning and education, not financial, tax, legal or medical advice.
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