Measuring

Square Footage Calculator

Find the area of any room, patio or yard in square feet, square yards and square meters. Add rectangles, triangles and circles, and subtract the parts you will not cover.

Units

Split an odd-shaped space into rectangles, triangles and circles. Use decimals for inches (10 ft 6 in = 10.5 ft).

Enter your measurements and press Calculate.

How we calculate

Every area is worked out with standard geometry, then added together. Rows you mark as “Subtract” are taken away, for example a kitchen island or a fireplace hearth you will not cover.

Rectangle: area = length x width Triangle: area = 1/2 x base x height Circle: area = 3.14159 x (diameter / 2)^2 Total = sum of added areas – sum of subtracted areas

Conversions: 1 square yard = 9 square feet; 1 acre = 43,560 square feet; 1 foot = 0.3048 meters exactly, so 1 square meter = about 10.764 square feet.

Worked example

A 12 x 15 ft bedroom: 12 x 15 = 180 sq ft (20 sq yd, or about 16.72 sq m).

A round patio 10 ft across: radius = 5 ft, so 3.14159 x 5 x 5 = 78.54 sq ft.

An L-shaped room with a triangle bay and a built-in cabinet: main rectangle 20 x 10 = 200 sq ft, plus a triangle with a 10 ft base and 6 ft height = 30 sq ft, minus a 3 x 4 ft cabinet = 12 sq ft. Total: 200 + 30 – 12 = 218 sq ft.

A 15 by 12 foot room split into one rectangle180 sq ft15 ft12 ft
Length x width: 15 ft x 12 ft = 180 square feet.

How to measure a space

  • Use a tape measure (or a laser measure) and write every number down as you go.
  • Measure wall to wall at floor level. Round to the nearest inch, then convert inches to decimal feet (6 in = 0.5 ft, 3 in = 0.25 ft).
  • Sketch the space and split it into rectangles, triangles and circles. Enter each one as its own row.
  • For a circle, measure straight across the widest point: that is the diameter.
  • Subtract anything you will not cover, such as a kitchen island.
  • When you buy flooring, sod or paint, add extra for cuts and waste. The product label or your supplier will tell you how much.

FAQ

How do I find the square footage of a room?

Multiply the length by the width, both in feet. A 10 by 12 ft room is 10 x 12 = 120 square feet. For odd shapes, split the room into simple shapes and add them up.

How do I convert inches to feet for this calculator?

Divide inches by 12. For example 8 inches is 8 / 12 = 0.67 ft, so 10 ft 8 in is about 10.67 ft.

How many square feet are in a square yard or an acre?

A square yard is 3 ft x 3 ft = 9 square feet. An acre is 43,560 square feet.

How do I measure a triangle?

Measure the base (one side) and the height: the straight-line distance from the base to the opposite corner, at a right angle to the base. Area is half of base times height.

Can I use meters?

Yes. Switch the Units toggle to Metric and enter meters. Any numbers you already typed are converted for you.

Part of our outdoor-career toolkit: From office to outdoors.

Estimates only. Results are estimates based on the measurements you enter. Check local building codes and your product labels, confirm quantities with your supplier, and buy a little extra material. This is not professional or structural advice. Last checked: September 27, 2026.

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