Square Footage Calculator — Rooms, Floors and Plots
0 rooms counted · average 0.00 ft² · largest 0.00 ft²
- Square metres
- 0.00 m²
- Square yards
- 0.00 yd²
- Square inches
- 0 in²
- Acres
- 0
One or more rooms are incomplete and are not included in the total.
0.00 m
0.00 m² — before doors and windows
0' on each side
0.00 m² · 0.00 ft² of that is the allowance
Materials estimate
Always rounded up
Keep a box for repairs
Waste included
Enter the length and width of a room and this calculator gives you the area in square feet, square metres, square yards, square inches, and acres at once. Add a row for every room and it keeps a running project total, which is the number a flooring quote is actually built on. Five shapes are covered — rectangles, L-shaped rooms, circles, triangles, and trapezoids — and the materials panel turns the total into boxes to buy and a cost, with a waste allowance on top. Nothing is uploaded; the measurements stay in your browser.
Common room sizes in square feet
Dimensions in feet, area rounded, and the order quantity a 10% waste allowance implies. Handy for sanity-checking a quote before you measure anything.
| Room | Square feet | Square metres | Order with 10% waste |
|---|---|---|---|
| 8 × 10 | 80 ft² | 7.43 m² | 88 ft² |
| 10 × 10 | 100 ft² | 9.29 m² | 111 ft² |
| 10 × 12 | 120 ft² | 11.15 m² | 132 ft² |
| 12 × 12 | 144 ft² | 13.38 m² | 159 ft² |
| 12 × 14 | 168 ft² | 15.61 m² | 185 ft² |
| 12 × 16 | 192 ft² | 17.84 m² | 212 ft² |
| 14 × 16 | 224 ft² | 20.81 m² | 247 ft² |
| 15 × 20 | 300 ft² | 27.87 m² | 330 ft² |
| 16 × 20 | 320 ft² | 29.73 m² | 352 ft² |
| 20 × 24 | 480 ft² | 44.59 m² | 528 ft² |
Area unit conversions
Every figure below comes from one fact: the international foot has been exactly 0.3048 metres since the 1959 agreement, so a square foot is exactly 0.09290304 m². Nothing here is an approximation except the rounding.
| Unit | In square feet | Also equals |
|---|---|---|
| 1 square foot | 1 | 0.0929 m² · 0.1111 yd² · 144 in² |
| 1 square metre | 10.7639 | 1.196 yd² · 10,000 cm² |
| 1 square yard | 9 | 0.8361 m² · 1,296 in² |
| 1 square inch | 0.006944 | 6.4516 cm² |
| 1 acre | 43,560 | 4,046.86 m² · 4,840 yd² |
| 1 hectare | 107,639 | 10,000 m² · 2.471 acres |
| 1 square (roofing) | 100 | 9.29 m² — how shingles are sold |
How much waste to allow
The allowance pays for cuts you cannot reuse. Pattern and plank length drive it more than room size does: a long plank cut to fit a 2-foot gap leaves a 6-foot offcut that fits nowhere.
| Material and layout | Typical allowance |
|---|---|
| Laminate, click vinyl (straight lay) | 5–8% |
| Solid or engineered hardwood | 10% |
| Tile, straight grid | 10% |
| Tile, diagonal or herringbone | 15–20% |
| Carpet (roll goods, 12 ft wide) | 10–20% |
| Sheet vinyl | 10–15% |
| Sod and turf | 5–10% |
| Concrete slab | 5–10% |
A worked example: three rooms, one order
A living room 17 × 12'6", a bedroom 11 × 10, and an L-shaped kitchen 20 × 15 with a 7 × 5 corner taken out for the pantry. All three get the same laminate, sold in 23.8 ft² boxes at $62.
Living 17 × 12.5 = 212.50 ft²
Bedroom 11 × 10 = 110.00 ft²
Kitchen 20 × 15 − 7 × 5 = 265.00 ft²
total = 587.50 ft² (54.58 m²)
+ 10% allowance = 646.25 ft²
646.25 / 23.8 = 27.15 → 28 boxes
28 × 23.8 ft² = 666.40 ft² covered
28 × $62 = $1,736 ($2.95 per finished ft²)Two things worth noticing. The 12'6" has to be entered as 12.5, not 12.6 — typing 12.6 would add 1.7 ft² to the living room, which sounds trivial until the same slip is repeated across a floor plan. And the rounding up to 28 boxes leaves 78.9 ft² spare, which is 13% of the floor rather than the 10% you asked for. That is normal and it is the right way round: boxes come in whole numbers, and running one plank short in month two of a discontinued dye lot is a much more expensive problem than one surplus box.
If you are converting the plan itself rather than the floor, the Unit Converter handles length and area units side by side, the Percentage Calculator will work the allowance backwards from a quote, and for a triangular plot defined by angles rather than three sides the Triangle Calculator solves it properly.
Measuring well enough to trust the number
- Measure at the floor, not at waist height. Walls bow, and baseboards eat half an inch a side.
- Take the length twice, at both ends of the room. Rooms are rarely square; use the larger figure, because flooring has to reach the wide end.
- Round each measurement up to the next inch, never down. You cannot stretch a plank.
- Measure doorways and thresholds separately and add them as their own small rooms — a standard 36-inch doorway is about 2.5 ft² and is usually forgotten.
- For a plot, pace it out once before you trust the tape: a normal adult stride is close to 2.5 feet, so 40 paces is roughly 100 feet, enough to catch a decimal point in the wrong place.
How it works
- 1 Pick a shape and a unit Most rooms are rectangles, so that is the default. Switch to L-shaped for a room with a chimney breast or a kitchen return, or to circle, triangle, or trapezoid for an awkward plot. Choose whether you measured in feet, feet and inches, inches, yards, metres, or centimetres.
- 2 Type the measurements Fill in every box the shape asks for. If you picked feet and inches you get a second, narrow box for the inches — enter 12 ft 6 in as 12 and 6 rather than typing 12.6, which is a different length and the most common square footage mistake there is.
- 3 Add the rest of the rooms Press Add a room for each extra space, and set the quantity if several rooms are the same size. The project total at the top adds every valid row and shows what share each room contributes.
- 4 Estimate the materials Set a waste allowance — 10% for a straight lay, 15–20% for diagonal or herringbone tile — then enter the coverage printed on the box and its price. You get whole boxes to buy, the leftover area, and a delivered cost per square foot.
- 5 Add a ceiling height for paint The optional ceiling height turns each room's perimeter into wall area, which is what paint coverage is quoted against. Subtract roughly 20 ft² for each door and 15 ft² for each window before you buy.
Your data stays private
All processing happens entirely in your browser. No files, text, or data are ever sent to our servers. You can disconnect from the internet and this tool will still work.
Frequently asked questions
- How do I calculate the square footage of a room?
- Measure the length and the width in feet and multiply them. A room 12 feet by 14 feet is 168 square feet. If your tape reads feet and inches, convert the inches to a decimal first by dividing by 12 — 12 ft 6 in is 12.5 ft, not 12.6 — or use the feet-and-inches mode on this page and let it do that step.
- How do I work out an L-shaped room?
- Measure the overall length and width as if the room were a full rectangle, then measure the missing corner and subtract it. The L-shaped option here does exactly that. One useful quirk: an L made by removing a corner has the same perimeter as its bounding rectangle, because the two cut edges are exactly as long as the two they replace — so your baseboard figure does not change.
- How many square feet is a 12x12 room?
- 144 square feet, or 13.38 square metres. That is also 16 square yards, which is how carpet used to be quoted in the US and still is in parts of the UK. With a 10% waste allowance you would order about 159 square feet of flooring.
- How do I convert square feet to square metres?
- Divide by 10.7639, or multiply by 0.0929. The number comes from the foot being exactly 0.3048 metres since 1959, so a square foot is 0.3048² = 0.09290304 m². Going the other way, multiply square metres by 10.7639. A 1,500 ft² apartment is 139.35 m².
- How much extra flooring should I buy for waste?
- 10% is the standard allowance and covers a straight lay in a plain rectangular room. Go to 15–20% for diagonal or herringbone patterns, for planks longer than 48 inches, and for rooms with lots of alcoves, since every cut leaves an offcut too short to use. Keep a full box after the job — three years later the same batch and dye lot will be discontinued.
- Does square footage include closets, hallways, and stairs?
- For a flooring order, measure every surface you intend to cover, closets and hallways included — a walk-in closet is 20 to 40 square feet of real flooring. For a property listing in the US, the ANSI Z765 standard counts finished space measured to the outside of the exterior walls, excludes anything below grade from the headline figure, and counts a staircase once, on the floor it descends from.
- How do I calculate square footage for paint instead of floor?
- Paint covers walls, so you need the perimeter times the ceiling height, not the floor area. Enter a ceiling height and the wall-area readout appears. Then subtract about 20 square feet for each door and 15 for each standard window. One US gallon covers roughly 350–400 ft² per coat, so a 12 × 14 room with 9-foot ceilings needs about 468 ft² of wall, two coats, three gallons.
- What is the difference between square feet and feet squared?
- In everyday use they get swapped freely, but they are not the same thing. 10 square feet is an area of ten one-foot tiles. 10 feet squared is a 10-by-10 room, which is 100 square feet — ten times bigger. The ambiguity matters most when someone quotes a price in 'feet squared'; ask which they mean.
- How many square feet are in an acre?
- 43,560. The number looks arbitrary and is: an acre was a chain by a furlong, 66 feet by 660 feet, the strip a team of oxen could plough in a day. A square acre is about 208.7 feet on a side. For plots, enter the dimensions in feet or yards and read the acres row.
- Can I use this for a roof?
- For a flat or very shallow roof, yes. For a pitched roof you need the slope factor: multiply the footprint by 1.031 for a 4/12 pitch, 1.118 for 6/12, and 1.25 for 9/12. Roofing is also sold in 'squares' of 100 ft², so divide the result by 100 and round up, then add 10% for ridge, valleys, and starter course.
- Is anything I measure sent to a server?
- No. Every calculation runs in JavaScript inside your browser. Your room list is kept in your own browser's local storage so it survives a refresh, and nothing else ever sees it — no account, no upload, no logging.