Square footage calculator

How to calculate square footage

To calculate square footage, measure each part of the space in feet, find each part's area with the formula for its shape, and add the parts. Rooms are rarely one clean rectangle, so split L-shapes, bays and alcoves into simple pieces first.

Total = area 1 + area 2 + area 3 + …308 + 132 + 12 = 452 sq ft

Measurements in feet and inches need converting first: divide the inches by 12. A wall 11 ft 6 in long is 11.5 ft; 9 ft 3 in is 9.25 ft. Measure wall to wall at floor level and round to the nearest inch, not the nearest foot: on a 12 × 14 room, being half a foot short on each side drops the result by about 13 sq ft.

Common room sizes in square feet

A 12 × 12 ft room is 144 sq ft, or 16 sq yd. The same arithmetic for other common room sizes:

Square feet to square yards and square meters

One square yard is 9 square feet, and one square foot is 0.09290304 square meters exactly. The metric factor follows from the definition of the foot: since 1959 the international foot has been exactly 0.3048 meter, and the U.S. survey foot, a hair longer, has been obsolete since January 1, 2023.^[1] NIST's conversion tables list 9.290 304 × 10⁻² m² per square foot and 8.361 274 × 10⁻¹ m² per square yard.^[2]

Carpet and some flooring are still sold by the square yard; tile and hardwood by the square foot or by the box. For tile, the tile calculator turns square footage into pieces and boxes, and the grout calculator sizes the grout for the same floor.

Square footage of a house

A house's square footage is the finished living area, measured with a consistent method; it is not the sum of every room you could measure. For appraisals of single-family homes, Fannie Mae requires appraisers to follow the ANSI Z765-2021 standard when they measure and report above-grade and below-grade square footage. A level counts as below grade if any part of it is below grade, and below-grade area is reported separately from the above-grade total.^[3]

• Above-grade finished area is the figure most listings and appraisals lead with.
• Basements and partly below-grade levels are reported on their own line, even when finished.^[3]
• Your own estimate from room-by-room measurements will come out lower than an exterior-based figure, because it leaves out wall thickness, closets you skip and stair openings.

You can check the figure an appraiser used. When you apply for a mortgage secured by a first lien on your home, the lender must give you a copy of every appraisal and written valuation, free of charge, promptly upon completion or three business days before closing, whichever is earlier.^[4] The CFPB adds that if you have not received it, you can ask the lender for it.^[5] Compare its above-grade square footage with your own measurements before you rely on it.

Deducting islands, stairs and openings

Set an area to Deduct (rectangle) to subtract something inside the room you measured: a kitchen island you will not floor under, a stair opening, a built-in cabinet or a fireplace hearth. A 20 × 15 ft kitchen with a 4 × 6 ft island is 300 − 24 = 276 sq ft of floor to cover. Bay windows and round rooms go in as half circles and circles, measured by their diameter.

Price per square foot

Price per square foot is the total price divided by the square footage, and it is how most home costs are compared. NAHB's 2024 builder survey is an example: an average construction cost of $428,215 for 2,647 sq ft of finished area works out to $161.77 per square foot, which NAHB rounds to $162.^[6]

Price per sq ft = total price ÷ square feet$428,215 ÷ 2,647 = $161.77

The figure is only comparable when both sides measured the same way: a contractor's flooring price per square foot applies to the floor area you will cover, while a home's price per square foot uses its finished living area.

Why square footage drives project costs

Most home-cost figures are quoted per square foot, so an error in the area becomes an error in the budget. In NAHB's 2024 builder survey, the average new single-family home had 2,647 sq ft of finished area and cost about $162 per square foot to build, before the lot.^[6] Those per-square-foot figures only mean something if your square footage is measured the same way; the cost to build a house calculator and the home replacement cost calculator both start from finished area.

For smaller jobs, the Census Bureau's 2023 American Housing Survey found a median of $3,000 per flooring, carpeting or ceiling job among owner-occupied homes (average $4,829).^[7] Enter a price per square foot from your own quote in the calculator to turn your area into a cost, and if the project needs financing, compare options with the home improvement loan calculator.

Worked example: an open-plan living and dining area

1. Living area: 22 ft × 14 ft = 308 sq ft.
2. Dining area: 12 ft × 11 ft = 132 sq ft.
3. Angled bay: a triangle with an 8 ft base and 3 ft depth = ½ × 8 × 3 = 12 sq ft.
4. Total: 308 + 132 + 12 = 452 sq ft = 50.22 sq yd = 41.99 m².

If the space also had a round 8 ft reading nook, area 4 set to Circle with an 8 ft diameter would add 50.3 sq ft.