Measuring a room to work out roughly what a floor will cost is straightforward, and worth doing before you get quotes so you know what ballpark you are in. Measuring precisely enough to order materials is a different job — here is how to do the first properly and why you should leave the second to the fitter.
The basic method
Measure the length and width of the room at its widest points, including any doorway recesses, alcoves and bay windows. Always measure into the doorway to where the flooring will stop — usually the centre of the closed door — because that strip is real material.
Multiply length by width for the square metre figure. Round each measurement up to the nearest 10cm; you cannot buy a partial plank and it is better to be slightly over than a metre short on delivery day.
Measure in two places for each dimension, at opposite ends of the room. In older houses in Bexley, Dartford or Greenwich, rooms are very often out of square by 5–10cm across a modest room, and using the smaller figure guarantees a shortfall.
Awkward shapes
For an L-shaped room, split it into two rectangles, measure each separately and add the totals. Draw a quick sketch with the measurements on it — you will need it when discussing the job with a fitter, and it prevents the classic error of double-counting the overlap.
Bay windows are measured as a separate rectangle taken to the deepest point of the bay, then added. Do not try to calculate the true angled shape; the material comes in rectangles regardless and the offcuts are usually unusable.
Chimney breasts and fitted cupboards can be deducted, but only if they are more than about half a square metre and only if the floor genuinely stops at them. In practice, ignoring small obstructions is safer — the material still has to be cut around them, and the cut-out is waste either way.
Adding a waste allowance
Every floor needs a waste allowance for cuts, pattern matching and errors. For straight-plank LVT or laminate in a simple rectangular room, add 7–8%. For a complex room shape, a diagonal lay, or a floor with a strong pattern to match, add 10–12%. For herringbone or chevron, add 12–15%.
Carpet works differently because it comes in rolls of fixed width — usually 4m or 5m. A room 4.2m wide needs a 5m roll, and the 0.8m strip is waste even though you paid for it. This is why carpet is priced by the linear metre of roll, and why a slightly narrower room can be significantly cheaper.
Sheet vinyl follows the same roll logic, typically in 2m, 3m and 4m widths. In a small bathroom this usually means buying a piece larger than the room, which is unavoidable and is what makes the seamless result possible.
- Straight planks, simple room: +7–8%
- Diagonal lay or strong pattern: +10–12%
- Herringbone or chevron: +12–15%
- Carpet and sheet vinyl: calculated by roll width, not area
Stairs and landings
Stairs are measured by the step, not by area. For each step, measure the tread depth plus the riser height, add about 25mm for the nosing, and multiply by the number of steps. A typical UK straight flight of 13 steps needs roughly 4.5–5 linear metres of a 1m-wide strip.
Winder steps — the wedge-shaped ones on a turn — take considerably more material because each is cut individually to a triangle. Allow roughly double a straight step for each winder.
The landing is measured as a normal room, but do not forget the return nosing at the top of the flight and any spindle cut-outs, which add both material and labour.
Things people forget
The doorway strip. Flooring runs into the door opening to the centre of the door. Across a house with eight doorways that is close to a square metre.
Under-radiator areas. The floor continues under radiators, and cutting around pipe legs is fiddly labour as well as material.
Threshold and trim lengths. Measure the linear metres of doorway thresholds, beading and any stair nosings — they are quoted separately and it is easy to under-order.
Direction of lay. Planks generally run along the longest dimension of the room, or towards the main light source. Changing the direction changes the waste percentage, sometimes materially in a long narrow room.
Finally: a fitter will always re-measure before ordering. Your figure is for budgeting and comparison; theirs carries the responsibility for the material being right. Never order flooring from your own measurements unless you are fitting it yourself.
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Frequently asked questions
How do I calculate how much flooring I need?
Multiply the room's length by its width at the widest points, including doorway recesses, then add a waste allowance — 7–8% for straight planks in a simple room, 12–15% for herringbone.
How much waste should I allow for flooring?
7–8% for straight-plank floors in rectangular rooms, 10–12% for diagonal or strongly patterned lays, and 12–15% for herringbone or chevron patterns.
How do you measure stairs for carpet?
Per step: tread depth plus riser height plus about 25mm for the nosing, multiplied by the number of steps. Winder steps need roughly double a straight step because each is cut individually.
Should I measure the floor myself?
It is useful for budgeting and comparing quotes, but never order materials from your own measurements. A fitter will always re-measure and takes responsibility for the quantity being correct.