Square Footage Calculator
Measure any space in square feet — and any number of rooms at once. Add a row per area, pick its shape (rectangle, circle, triangle, trapezoid), and the calculator keeps a live running total. A 12 ft × 10 ft room is 120 ft². Add a waste factor and a price per ft² for an instant material estimate, with ft², in², yd², m² and acres shown together.
120 ft² total area
11.15 m² · 13.33 yd² · 17,280 in² · 0.0028 acres
Order with 10% waste: 132 ft²
≈ 1 gallon(s) of paint for one coat (350 ft²/gal).
Area uses standard geometry (rectangle L×W, circle πr², triangle ½·b·h, trapezoid ½(a+b)·h); 1 ft² = 0.0929 m². How we calculate →
How to calculate square footage
For a rectangular space, square footage is simply length × width with both measured in feet. A room that is 12 ft by 10 ft is 12 × 10 = 120 square feet. If you measured in inches, divide each side by 12 first, or use the unit dropdown above and the calculator converts for you. The result updates as you type — there's no Calculate button.
The same idea works for any rectangle: a 10 × 10 room is 100 ft², a 20 × 15 room is 300 ft². The calculator keeps the answer in square feet and also shows it in square inches, square yards, square metres and acres at the same time.
Irregular and L-shaped rooms
Real rooms are rarely a single neat rectangle. The reliable method is to split the space into simple shapes, measure each one, and add the areas together. An L-shaped room is just two rectangles; a room with a bay window is a rectangle plus a trapezoid or a half-circle.
That's exactly what the “Add area / room” button does: add a row for each part of the space (or each room in a house), pick its shape, and the calculator keeps a running total. Most calculators only handle one shape at a time and force you to add things up by hand — here the cumulative total is live.
Circles, triangles and trapezoids
Not everything is square. The calculator includes the standard area formulas: a circle is π × radius² (enter the diameter and it halves it for you), a triangle is ½ × base × height, and a trapezoid is ½ × (side a + side b) × height. Pick the shape from the dropdown and only the fields you need appear.
Combine them freely — a patio that is a rectangle with a semicircular end is one rectangle row plus one circle row at half quantity. The total still lands in square feet.
Converting between square feet, yards, metres and acres
The conversions are fixed factors. 1 square yard = 9 square feet, so divide square feet by 9 to get square yards (carpet is often priced this way). 1 square foot = 0.0929 square metres, and 1 acre = 43,560 square feet. The calculator shows all of these at once so you never have to look up a factor — useful when flooring is quoted per square yard but you measured in feet.
Measuring the square footage of a house
To find a whole home's finished area, measure each room's length and width, add a row per room, and read the total. Conventionally, finished, heated living space counts toward square footage; garages, unfinished basements and open-to-below voids usually don't, which is why a listing's number can differ from a tape-measure total. For a quick whole-house figure, measuring the outside footprint per floor and subtracting garage and porch areas is a common shortcut.
Flooring cost, paint and the waste factor
Once you know the area, multiply by the price per square foot to estimate material cost — enter it above and the calculator does it. Always order extra for offcuts and mistakes: a waste factor of about 10% for straight layouts and 15% for diagonal or patterned ones is typical, and the tool adds your chosen percentage to the order quantity. For paint, one gallon covers roughly 350 ft² per coat, which the calculator estimates automatically.
Frequently asked questions
How do I calculate square footage?
For a rectangle, multiply length by width with both in feet: a 12 ft × 10 ft room is 120 square feet. For other shapes use the standard formulas (circle πr², triangle ½·base·height, trapezoid ½(a+b)·height). Enter your measurements above and the area is shown instantly in ft², yd², m² and acres.
How do you calculate the square footage of an irregular or L-shaped room?
Split the space into simple shapes, measure each, and add the areas together. An L-shape is two rectangles. Use the “Add area / room” button to add a row per part of the space — the calculator keeps a live running total so you don't have to add them up by hand.
How many square feet is a 10x10 room?
A 10 ft by 10 ft room is 10 × 10 = 100 square feet. A 12 × 12 room is 144 ft², and a 10 × 12 room is 120 ft².
How do you convert square feet to square yards?
Divide square feet by 9, because 1 square yard equals 9 square feet. For example, 180 ft² ÷ 9 = 20 square yards. The calculator shows square yards automatically alongside square feet.
How do I calculate square footage from inches?
Convert each measurement to feet first by dividing by 12, then multiply. Or just select “Inches” in the unit dropdown and enter the values in inches — the calculator converts and returns the area in square feet. (Multiplying two inch measurements gives square inches; divide by 144 to get square feet.)
How much does flooring cost per square foot?
It varies by material — roughly $1–$5/ft² for laminate or vinyl and $3–$15/ft² for hardwood or tile, plus installation. Enter your price per square foot above and add a 10–15% waste factor; the calculator estimates the material cost on the order quantity.
How do you measure the square footage of a house?
Measure each room's length and width, add a row per room, and read the total. Finished, heated living space counts; garages and unfinished areas usually don't, so a tape-measure total can differ from a listing figure.
How many square feet are in an acre?
One acre is 43,560 square feet. So a 1,000 ft² space is about 0.023 acres. The calculator shows acres automatically for large areas like lots and yards.
Researched & verified by the Calcuris Data & Research Team. How we build and check our tools →