How to measure a room for flooring (including L-shapes and alcoves)

To measure a room for flooring: measure the length and width in metres at floor level, each at two different points along the wall, use the larger figure of each pair, and multiply them for the area in m². If the room is not a simple rectangle, split it into rectangles, measure each one, and add the areas together. That is the whole method. The rest of this guide covers the details that catch people out: alcoves, L-shapes, out-of-square walls, and what not to subtract.

What should you measure with?

A steel tape measure is fine for one room; a laser measure is faster, easier on long spans (no sag, no helper needed), and typically accurate to a couple of millimetres. Whichever you use:

• Measure at floor level, not waist height, because walls lean, and the floor is where the flooring goes.
• Measure in metres to two decimal places (for example 4.27 m). Flooring is sold by the square metre, so working in metres avoids conversion mistakes.
• Write measurements on a sketch of the room as you go. Memory is not a measuring tool.

Why measure every wall twice?

Because rooms are rarely square. Measure the width at both ends of the room: if you get 3.62 m at one end and 3.58 m at the other, your walls are 40 mm out of parallel, and that has two consequences:

1. Buy with the larger number. Material has to cover the widest point.
2. Expect a tapered cut. The row along one wall will need to be cut at a slight angle rather than a straight rip. Knowing this in advance lets you choose which wall gets the taper: pick the one behind furniture or where the light does not rake along the joint.

A quick diagonal check tells you the same story: measure both diagonals of the room. In a true rectangle they are equal; a difference of more than a couple of centimetres means at least one corner is not 90°.

How do you measure an L-shaped room?

Split it into two rectangles and add them. For an L-shaped room where the full outer dimensions are 5 m × 4 m, with a 2 m × 1.5 m corner missing:

• Option 1, add the parts. Rectangle A: 5 × 2.5 = 12.5 m². Rectangle B: 3 × 1.5 = 4.5 m². Total: 17 m².
• Option 2, subtract the notch. Full rectangle: 5 × 4 = 20 m². Missing corner: 2 × 1.5 = 3 m². Total: 20 - 3 = 17 m².

Do it both ways. If the two answers disagree, one of your measurements is wrong, and it is far cheaper to find that out now. The same splitting method handles T-shapes (three rectangles) and U-shapes (three or four).

Alcoves, bays, doorways and chimney breasts

• Alcoves (for example either side of a chimney breast): each alcove is a small rectangle of extra floor. Measure its width and depth and add it.
• Bay windows: measure the containing rectangle of the bay and add it. For an angled or curved bay, this slightly over-measures, which is good, because the excess covers the angled cuts the bay will demand.
• Doorways: flooring usually runs to the middle of the door threshold. It is a tiny area, but count it, because it is at the trim-critical edge of the room.
• Chimney breasts and fixed built-ins: you can subtract them, but for anything under about a square metre it is safer not to. The uncounted area quietly pads your waste allowance, and cutting around obstacles generates extra waste in exactly that spot.
• Kitchen units and wardrobes: floating floors should not be trapped under heavy fixed units, so flooring normally stops at the plinth. Measure to the front of fixed units, not the wall behind them.

What about angled walls?

For a wall that cuts across a corner at an angle, measure the containing rectangle as if the angle were not there. The triangle you have over-counted becomes waste allowance, and angled walls genuinely produce more waste, because every board meeting them needs a mitred cut whose offcut is rarely reusable. If a large part of the room is angled, mention it when choosing your waste percentage: it is one of the things that pushes you to the top of the range in the flooring waste percentage table.

From measurements to a shopping list

Once you have the area, the remaining steps are adding the right waste allowance for your pattern and converting to packs, both covered with worked examples in how much flooring do I need? and how many packs of laminate.

Or skip the arithmetic: draw the room, L-shape, alcoves, angled walls and all, in Floor Optimizer, and it computes the area, simulates the board layout in your chosen pattern, and returns the exact number of boards to buy, with every measurement you took doing real work instead of feeding a rule of thumb.