📐 Square Footage Calculator
Measure a room in feet or metres, add the waste allowance your material needs, and get the area plus what it will cost at your price per square foot or per square metre.
Measuring a room, allowing for waste, and pricing the job
Square footage is length times width, and that part is easy. What separates a correct order from an expensive one is everything around it: measuring the right thing, handling rooms that are not rectangles, and adding the waste allowance your particular material needs.
Measure this, not that
- Measure at floor level, wall to wall, not at waist height where skirting and radiators get in the way.
- Check the diagonals. In a true rectangle they are equal. If they differ by more than a centimetre or two, the room is out of square and you will need more material than the simple calculation suggests.
- Include doorways and thresholds if the flooring runs through them.
- Do not subtract small obstacles. Kitchen islands and built-in units usually still need material cut around them, so subtracting the footprint leaves you short.
Rooms that are not rectangles
Split the space into rectangles, measure each, and add. An L-shaped room is two rectangles; a room with a bay is a rectangle plus a partial circle or trapezoid. Draw it on paper first with the measurements written on, because the common failure is not the arithmetic but losing track of which measurement belongs to which section.
For genuinely curved walls, approximate with a series of narrow rectangles, or treat the curve as a circle sector and use πr² × angle/360.
Waste allowances by material
| Material and layout | Waste allowance |
|---|---|
| Sheet vinyl, straight lay, simple room | 5% |
| Laminate or engineered wood, straight | 7–10% |
| Ceramic or porcelain tile, straight | 10% |
| Tile laid diagonally | 15% |
| Herringbone or chevron patterns | 15–20% |
| Carpet, from a roll | 10–15% depending on roll width |
| Patterned material needing repeat matching | 15–20% |
Order the waste in the same batch. Tile and laminate are produced in dye lots, and a second order weeks later can arrive a visibly different shade. Keeping a few spare pieces after the job is also worth doing, for the repair you will need in three years.
Square feet and square metres
1 m² = 10.764 ft² 1 ft² = 0.0929 m²
Flooring is sold by the square metre in most of the world and by the square foot in the US, and quotes frequently mix them. Always confirm which unit a price refers to: a material at $4.50 per square foot is $48.44 per square metre, and confusing the two is a tenfold error in either direction.
Boxes, not square feet
Most hard flooring is sold by the box, covering a fixed area. Divide your total including waste by the coverage per box and round up, always up. A room needing 169 ft² with boxes covering 23.5 ft² needs 169 / 23.5 = 7.2 boxes, so eight. That rounding is itself an extra 4% of waste, which is worth knowing before you add a generous allowance on top of it.
Beyond flooring
The same measurement answers several other questions. Paint coverage is typically 10 to 12 m² per litre per coat, so a 30 m² room with 70 m² of wall needs about 12 litres for two coats. Underlay, insulation and turf are all priced by area. Heating output is commonly estimated per square metre of floor area, though volume and insulation matter more.
A worked example
A living room 14 ft by 11 ft, laying porcelain tile straight. Floor area is 154 ft². At a 10% allowance that is 169.4 ft², which is 15.74 m². At $4.50 per square foot the material comes to $762, of which $69 is the waste allowance. If the tile comes in boxes of 15 ft², you need 12 boxes, covering 180 ft².
Frequently Asked Questions (FAQs)
How do I calculate square footage?
Multiply length by width in feet. For a room 14 by 11 feet, that is 154 square feet. If you measured in inches, divide the result by 144; if in metres, multiply the square metres by 10.764.
How much waste should I add?
Five per cent for simple straight-lay sheet material, 10% for most tile and laminate, and 15% or more for diagonal and herringbone patterns or anything with a pattern repeat. Rooms with many cuts and alcoves need the higher end of each range.
How do I measure an L-shaped room?
Split it into two rectangles along the inside corner, measure each separately and add the areas. Draw the plan and write the measurements on it before you start multiplying, because mixing up which number belongs to which rectangle is the usual error.
Should I subtract kitchen units or an island?
Generally not. Flooring usually has to be cut to fit around them, so the material is consumed regardless, and under-unit space is often floored anyway. Subtract only for genuinely large permanent fixtures that the flooring will not pass under.
How many square feet are in a square metre?
10.764. A 20 square metre room is 215 square feet. Make sure you know which unit a supplier's price uses, because the same number means a tenfold difference in cost.
How much paint do I need for the same room?
Measure the walls, not the floor: perimeter times height, minus doors and windows. Most emulsion covers 10 to 12 square metres per litre per coat, so divide the wall area by 11 and multiply by the number of coats.