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- Square footage is the area of a flat space in square feet.
- Rectangle: length × width. Triangle: ½ × base × height. Circle: π × radius².
- A 15 ft × 12 ft room is 180 square feet, which is 20 square yards.
- Use it for flooring, paint, carpet, rent, lot size and home listings.
How to use the square footage calculator
Pick the shape
Choose rectangle, triangle, circle, trapezoid or L-shape. Most rooms and lots are rectangles.
Choose your unit
Measure in feet, inches, yards, meters or centimeters. The result is always shown in square feet as well as other units.
Enter the sizes
Type the length and width, or the numbers the chosen shape asks for. For several identical rooms, change the quantity.
Read the area
You get square feet, square yards, square meters, acres and square inches. Add a price per square foot for a cost estimate.
How to calculate square footage
Measure each side in the same unit, find the area with the formula for the shape, then convert to square feet. For an irregular room, split it into rectangles and triangles, find each area and add them up.
Area formulas
Rectangle or square = length × width
Triangle = ½ × base × height
Circle = π × (diameter ÷ 2)²
Trapezoid = ½ × (side 1 + side 2) × height
L-shape = length × width − missing corner
Convert units first: 1 yard = 3 feet, 1 meter = 3.2808 feet and 1 inch = 1/12 foot.
Worked examples
A 15 ft × 12 ft room
Length times width.
180 ÷ 9 = 20 square yards, which is how carpet is often sold.
An L-shaped room
The full box is 15 ft × 12 ft and a 5 ft × 4 ft corner is missing.
Subtract the missing corner from the full rectangle.
A room measured in meters
4 m by 3 m is 12 square meters.
1 square meter is 10.764 square feet.
A circle and a triangle
A 10 ft round patio and a triangle with a 10 ft base and 8 ft height.
Use the calculator once for each part and add the totals.
Square footage conversion chart
Area units
Common conversions.
Use the calculator to convert any area.
Where a square footage calculator helps
Flooring and carpet
Find the area to order, then add waste with the tile calculator.
Paint and wall finishes
Work out the surface area you need to cover.
Real estate and rent
Compare homes, rooms and rent per square foot.
Concrete, gravel and mulch
Start with the area, then use the concrete calculator or the gravel calculator.
Measure at floor level and measure twice. For homes, the number on a listing may follow a local standard, for example living area that excludes the garage and unfinished space, so it may differ from your own tape measure. Always check with the appraiser or the listing rules for official figures.
Square footage calculator FAQ
How do I calculate the square footage of a room?
Multiply the length by the width, both in feet. A 15 ft by 12 ft room is 180 square feet.
How do I calculate the square footage of a house?
Find the area of each room or floor and add them up. Check whether you should include stairs, hallways and finished basements, because listing rules differ.
How do I convert square feet to square meters?
Multiply the square feet by 0.0929. For 180 square feet, that is about 16.72 square meters.
How do I find the square footage of an irregular shape?
Split it into rectangles, triangles and circles, calculate each, then add them. For an L-shape, subtract the missing corner from the full box.
How many square feet are in a square yard?
There are 9 square feet in a square yard, because 1 yard is 3 feet and 3 × 3 = 9.
How many square feet are in an acre?
There are 43,560 square feet in an acre.