How to use this calculator
- Choose the shape. Most rooms are rectangles, but triangles and trapezoids are useful for lots and gardens.
- Choose the unit you measured in: feet, inches, yards or meters.
- Enter the measurements for the shape.
- Read the area in all units at once. For an L-shaped room, calculate each rectangle and add the results.
How the numbers are calculated
A rectangle is length times width. A triangle is half of base times height. A circle is pi times the radius squared. A trapezoid is half the sum of the two parallel sides, times the height between them.
The result is converted to square feet. One square yard is 9 square feet, one square meter is 10.764 square feet, and one acre is 43,560 square feet.
Worked example
A room 14 ft by 12.5 ft is 175 sq ft. That is 19.44 square yards or 16.26 square meters. For a room 12 ft 6 in wide, write the width as 12.5 ft, because 6 inches is half a foot.
Tips before you buy
- Convert inches to decimal feet by dividing by 12, so 9 inches is 0.75 ft. Or set the unit to inches.
- Measure the widest points of the space, and measure twice.
- For rooms with closets or alcoves, split the space into rectangles and add them.
- Square footage used in real estate listings follows specific measurement standards that differ from a simple floor area.
- When you buy materials, add 5 to 15% for waste. See our flooring, drywall and sod calculators.
Frequently asked questions
How do I calculate the square footage of a room?
Multiply the length by the width, both in feet. A 12 ft by 15 ft room is 180 square feet.
How do I calculate an L-shaped room?
Split it into two rectangles, find the area of each, and add them together.
How do I convert square feet to square yards?
Divide the square feet by 9. A 180 square foot room is 20 square yards.
How many square feet are in an acre?
One acre is 43,560 square feet.
How do I measure a room with an alcove or bay window?
Treat the main room and the alcove as separate rectangles, calculate each area, and add them. For a bay with angled sides, split it into a rectangle and two triangles.
What is the difference between square feet and linear feet?
Square feet measure area, which is length times width. Linear feet measure length in a straight line. Flooring is priced per square foot, while trim and fencing are usually priced per linear foot.
Related calculators
These results are estimates for planning purposes. Material sizes, densities and local requirements vary, so confirm quantities with your supplier or a qualified contractor before ordering.
Last updated October 11, 2026.