How to Calculate Square Footage
Square footage is the number every material estimate starts from. Here is how to get it right for simple and awkward spaces.
Updated November 1, 2026
The basic method
- Measure the length of the space in feet.
- Measure the width in feet.
- Multiply them. The result is the area in square feet.
A room 14 ft long and 11 ft wide is 14 × 11 = 154 sq ft. Measure at floor level from wall to wall, and round to the nearest inch.
Converting inches
If a measurement has inches, turn them into a decimal of a foot by dividing by 12. A room that is 13 ft 9 in by 10 ft 4 in is 13.75 × 10.33 = 142 sq ft. Multiplying feet by inches directly is the most common mistake in area sums.
L-shaped and irregular rooms
Split the space into rectangles that do not overlap, measure each, and add the results.
| Part | Size | Area |
|---|---|---|
| A | 18 × 12 ft | 216 sq ft |
| B | 10 × 8 ft | 80 sq ft |
| Total | 296 sq ft |
For a space with a bump-out, it is sometimes quicker to measure the full rectangle and subtract the missing corner.
Circles and curves
The area of a circle is π × r², where r is the radius, half the diameter. A round patio 12 ft across has a radius of 6 ft, so its area is 3.1416 × 36 = 113 sq ft. For a half-circle bay, halve the result. For free-form garden beds, estimate an average width and length or split the shape into a few rectangles and triangles.
Triangles
Area = base × height ÷ 2. The height is measured at a right angle to the base, not along a sloping side. A gable wall 24 ft wide that rises 6 ft to the peak has a triangle area of 24 × 6 ÷ 2 = 72 sq ft.
Square footage of a house
For listings and appraisals, house size is normally measured from the outside walls and includes only finished, heated living space. Garages, unfinished basements and open porches are usually listed separately. Rules vary by country and region, so a real estate figure may differ from the sum of your room measurements.
Square feet to square metres
Multiply square feet by 0.0929 to get square metres, or divide square metres by 0.0929 to go back. 200 sq ft is 18.6 m². The square footage calculator converts both ways and handles circles and triangles.
Do the math for your project: open the square footage calculator.
Frequently asked questions
How do I calculate square footage in inches?
Multiply length by width in inches, then divide by 144 to get square feet.
Do I include closets in square footage?
For flooring, yes, if they get the same floor. For a house listing, closets inside finished living space are normally included.
How many square feet is a 10 × 12 room?
A 10 × 12 ft room is 120 square feet, or 11.15 square metres.