What the Square Footage Calculator does
This calculator adds up the square footage of a house, flat or project room by room. Each room can be a rectangle, an L-shape, a circle or a triangle, measured in feet and inches (12'6") or in metres; you can subtract cut-outs such as a kitchen island, add a waste allowance, and get the total in square feet and square metres with a cost at your price per square foot or per square metre.
Measurements are read the way people actually write them on a tape-measure sketch, so there is no need to convert 12 feet 6 inches to 12.5 first. The conversion between feet and metres uses the exact definition, 1 foot = 0.3048 metres. Everything is worked out in your browser and nothing you type is sent anywhere.
How to use it
- Measure each room wall to wall at floor level. For an L-shaped room, split it into two rectangles on your sketch and measure each one.
- Add one row per room. Pick the shape and the unit, then type the length and width -
12'6",12 ft 6 in,12.5,3.8 mor380 cmall work. The row's own area appears in a badge as soon as both numbers are in. - Use Add a cut-out for anything inside a room you do not want to cover: a fitted kitchen island, a hearth, a built-in wardrobe. Cut-outs are subtracted from the total.
- For a materials estimate, enter your price per square foot or per square metre and an extra percentage for waste and cuts. The result shows the area to buy and the estimated cost.
- Copy the summary, download the room-by-room table as CSV, or print it to take to a supplier.
Reading the results
The headline is the net floor area: all rooms added, cut-outs subtracted. It is the figure to use for flooring, paint for a floor or ceiling, underfloor heating or cleaning quotes.
"To buy with extra" is the net area plus your waste percentage. It is a purchasing figure, not the size of the room, and suppliers will usually round it up again to whole boxes or rolls.
Square yards are shown because carpet and some landscaping materials are priced that way in the US; 1 square yard is exactly 9 square feet.
Worked example: a living room, an L-shaped kitchen and a hallway
Living room 15' x 12' = 180 sq ft. The L-shaped kitchen splits into 12' x 10' = 120 sq ft and 6' x 4' = 24 sq ft, so 144 sq ft. The hall is 9'6" x 3'6", which is 9.5 x 3.5 = 33.25 sq ft.
The rooms add up to 357.25 sq ft. The kitchen island, 6' x 3' = 18 sq ft, is not getting new flooring, so it is subtracted: 339.25 sq ft net, which is 339.25 x 0.09290304 = 31.52 m².
Laminate is bought 10% over: 339.25 x 1.10 = 373.18 sq ft. At $4.50 per square foot the estimate is 373.175 x 4.50 = $1,679.29.
Formulas and scoring rules
- Rectangle
area = length × width- L-shape
area = (length_A × width_A) + (length_B × width_B)Split the L into two rectangles that do not overlap.- Circle
area = π × diameter² / 4- Triangle
area = base × height / 2The height is measured at right angles to the base.- Feet and inches
feet = feet + inches / 1212'6" = 12.5 ft. Fractions such as 6 1/2" are accepted.- Unit conversion
1 ft = 0.3048 m; 1 sq ft = 0.09290304 m²; 1 m² = 10.7639 sq ft; 1 sq yd = 9 sq ftExact international definitions; rounding to 2 decimals only for display.- Total and cost
net = Σ rooms − Σ cut-outs; to buy = net × (1 + waste% / 100); cost = to buy × price per unit area
Floor area is not the same as the advertised size of a home
Adding up the rooms gives the usable floor area of the spaces you measured. The square footage on a listing or a valuation is usually measured to a published standard - in the US often ANSI Z765 for single-family homes, internationally the IPMS or RICS codes, and in India carpet area, built-up area and super built-up area are separate figures defined in the real-estate regulations. These count walls, stairs, balconies and common areas differently, so your room-by-room total will rarely match the brochure.
For buying materials the room total is exactly what you want. For buying or renting a property, ask which measurement standard the quoted figure follows.
Limitations: what the result does not prove
- Curved walls, bay windows and irregular rooms are only as accurate as the shapes you split them into. Break an awkward room into several rectangles and triangles and add them as separate rows.
- It measures flat floor area. Sloping ceilings, stairs and wall area for paint or tiles need their own measurements.
- The waste allowance is your choice. Diagonal tile layouts, patterned carpet and many small rooms need more than a single open floor; check the manufacturer's guidance.
- Prices are whatever you type. The estimate excludes underlay, adhesive, trims, delivery and labour unless you include them in the price per unit area.
Privacy: where your data goes
Everything you paste, type or drop is processed in this browser tab. It is not uploaded, logged, stored or sent to analytics. Session recording and tag-manager scripts are switched off on this page.
Standards and sources
- NIST SP 811 - Guide for the Use of the International System of Units - checked 19 Sep 2026
- NIST Handbook 44 Appendix C - General tables of units of measurement
- International Property Measurement Standards (IPMS)
Frequently asked questions
How do I calculate the square footage of a room?
Multiply the length by the width in feet. A room 12 feet by 15 feet is 180 square feet. If you measured in feet and inches, type them as they are, such as 12'6", and the calculator converts the inches for you.
How do I work out square feet for an L-shaped room?
Divide the L into two rectangles that do not overlap, measure each one and add the two areas. Choose the L-shape option and enter both rectangles, or add them as two separate rooms.
How do I convert square feet to square metres?
Multiply square feet by 0.09290304, or divide by 10.7639. That factor is exact because one foot is defined as 0.3048 metres. The calculator always shows both units, so you never need to convert by hand.
How do I add up the square footage of a whole house?
Measure each room separately, add a row for each, and the calculator totals them. Include hallways and closets if they are getting the same flooring, and subtract fixed items such as kitchen islands as cut-outs.
Should I add a waste percentage to my square footage total?
Only when you are buying material to cover the area. The measured square footage is the true size of the room; for flooring or tiles add an allowance for cuts - often 5-10% for simple layouts and more for diagonal or patterned ones - and the calculator shows that purchase figure separately.
How do I find the square footage of a circle?
Measure the diameter across the widest point, square it, multiply by pi and divide by four. A 10-foot circular area is about 78.54 square feet. Choose the circle shape and enter the diameter.
Can I enter measurements in feet and inches like 12'6"?
Yes. It reads 12'6", 12' 6", 12'6, 12 ft 6 in, 12 feet 6 inches and fractional inches such as 6 1/2". A bare number uses the unit chosen for that row, feet or metres, and centimetres or millimetres can be typed with their unit.
Last reviewed by the A2Z.Tools team against the sources listed above.
