How do I calculate square footage?

Multiply the length by the width for a rectangular space, both measured in feet. A 12 ft by 15 ft room is 180 square feet. For anything that is not a plain rectangle, split it into shapes and add them together.

How many square feet are in a square yard?

Nine. A square yard is three feet by three feet, so divide square feet by nine to get square yards. The result panel shows both.

Should I include closets and doorways?

For flooring, yes: the covering usually runs into them. Measure the closet as its own small area and add it, rather than guessing at the extra.

Square Footage Calculator

Measure a room, a wall or a whole yard, add as many shapes as the space really has, and deduct anything that should not count. The total comes back in square feet, square yards and square metres at once.

Units

Feet & inches

Metric

Switching units keeps your measurements. Nothing is reset.

Areas

Shape

Length

Width

Diagram, not to scale

Deduct this area instead of adding it

Your result appears here

Enter your measurements to see how much material to buy.

How to use this calculator

1
Pick the shape that matches what you are measuring. Most rooms are rectangles; use a triangle or a trapezoid for a sloped end, and a circle for a round patio or pond.
2
Enter the measurements in feet and inches exactly as you took them. There is no need to turn 12 ft 7 in into a decimal.
3
Break an awkward space into pieces. An L-shaped room is two rectangles; add a second area rather than trying to average anything.
4
Tick the deduct box on anything that should be taken out of the total, such as a stairwell, a kitchen island or a fireplace hearth.

A worked example

A 12 ft × 15 ft living room plus a 4 ft × 10 ft hallway, with a 6 ft × 3 ft stairwell taken out:

Add the areas together
180 ft² + 40 ft²220 ft²
Deduct the openings
220 ft² − 18 ft²202 ft²
You will need
202 ft²

This example is produced by running the calculator above, so it always matches what the tool does.

The formula

A rectangle is length × width. A triangle is half the base times the height. A circle is π times the radius squared, where the radius is half the diameter you entered. A trapezoid averages the two parallel sides and multiplies by the height between them. Areas marked as deductions are subtracted from the total, which is never allowed to fall below zero.

Measuring well

Measure at the widest point

Rooms are rarely square. Measure each wall rather than assuming the opposite one matches, and use the larger figure if they differ, so you do not end up short.

Split, do not average

For an L-shape, a bay window or an alcove, add another area. Averaging two different widths quietly loses material in one corner and wastes it in another.

Decide whether to deduct at all

For flooring it is usually worth deducting a large fixed island or a stairwell, but not a small hearth: the offcuts are rarely reusable, and the deduction can leave you short.

Square feet, square yards and squares

Carpet is often quoted in square yards, which is nine square feet, and roofing in squares of one hundred square feet. Both are shown alongside the main total so nothing has to be converted twice.

Common questions

How do I calculate square footage?: Multiply the length by the width for a rectangular space, both measured in feet. A 12 ft by 15 ft room is 180 square feet. For anything that is not a plain rectangle, split it into shapes and add them together.
How many square feet are in a square yard?: Nine. A square yard is three feet by three feet, so divide square feet by nine to get square yards. The result panel shows both.
Should I include closets and doorways?: For flooring, yes: the covering usually runs into them. Measure the closet as its own small area and add it, rather than guessing at the extra.