Part of the square footage calculator set. Enter the length and width of up to six rooms in feet, feet + inches or meters, and the calculator adds them up into one total, with each room's share of the total shown below.
Updated September 2026 · Each room is treated as a rectangle.
| Room | Dimensions | Sq ft | Share |
|---|
Run a tape measure along the longest wall at floor level, then measure the wall at right angles to it — that gives you the length and width. Multiply the two together for the room's area: length × width. Measure closets and alcoves as their own rooms rather than guessing at how much they add to the main room, and enter each one as a separate room in the calculator above.
Work out each room's area on its own, then add the results — the calculator above does this for as many as six rooms at once. With the default example — a 12 ft × 10 ft room, a 14 ft × 12 ft room and a 10 ft × 8 ft room — the areas are 120 sq ft, 168 sq ft and 80 sq ft, which add up to 368 sq ft. That is 40.89 sq yd and 34.19 m², with an average room size of 122.67 sq ft. Room 1 makes up 32.6% of the total, Room 2 makes up 45.7%, and Room 3 makes up 21.7%.
A room that is not a plain rectangle — an L-shape, an alcove, a bay window — can still be measured this way: split it into two or more rectangles, work out each one, and add them together, exactly as the calculator adds up separate rooms. An L-shaped room made of a 12 ft × 10 ft section and a 6 ft × 4 ft section comes to 120 sq ft + 24 sq ft = 144 sq ft. Enter each section as its own room above to total an irregular space. For shapes other than rectangles — circles, triangles, trapezoids — the square footage calculator covers those formulas directly.
The total this calculator gives you is floor area — the figure you need for flooring, carpet or tile. Wall area, which is what you need for paint or wallpaper, is a different calculation: perimeter × ceiling height. A 12 ft × 10 ft room with an 8 ft ceiling has a perimeter of 2 × (12 + 10) = 44 ft, so its wall area is 44 ft × 8 ft = 352 sq ft — before subtracting doors and windows.
Measure the length and width in feet and multiply them: length × width. A 12 ft by 10 ft room is 120 sq ft.
Work out each room's area separately, then add the results. The default example above has three rooms of 120 sq ft, 168 sq ft and 80 sq ft, for a total of 368 sq ft.
A 10 ft by 12 ft room is 120 sq ft — 10 × 12.
Measure a closet separately from the room it opens onto, then add it as its own room here if flooring or paint is going into it. Treating it as a separate room keeps its dimensions accurate instead of guessing at an alcove.
The floor area of a 12 ft by 12 ft room is 144 sq ft — 12 × 12. Any waste allowance for cuts and offcuts is your flooring supplier's or installer's figure, not a fixed percentage, so check with them before ordering.
Divide square feet by 9. The default 368 sq ft total above is 368 sq ft ÷ 9 = 40.89 sq yd.
Calculate area for rectangles, circles, triangles and trapezoids, in feet, inches, yards or meters.
Divide a price by square footage, or compare two homes side by side.
Estimate roof area from the house footprint and pitch, plus roofing squares and shingle bundles.