How to measure a room for flooring
By Michał Białas · Last updated
Measure every wall at floor level, take the longest reading when walls aren’t parallel, and split odd shapes into rectangles or walk the walls one by one. Write down door widths and anything fixed to the floor, because they change the trim and sometimes the area.
What you need to write down
Every material on a flooring list comes from three numbers: the floor area, the perimeter and the length of wall that gets baseboard. Tile, planks, thinset, grout, leveler and underlayment follow the area. Baseboard, edge strip and sealing tape follow the perimeter. Door widths are subtracted from the baseboard and decide how many transition strips you need.
- A tape measure of at least 25 ft (8 m), or a laser distance meter for long rooms.
- A sketch of the room, even a rough one, with every wall numbered.
- The width of each doorway, measured between the door jambs.
- The size of anything that stays in place: a kitchen island, a tub, a shower base, built-in cabinets.
Rectangular rooms
Measure the length and the width at floor level, not at waist height where baseboard and cabinets get in the way. Take each measurement at both ends and in the middle. Old houses are rarely square, and a room can easily be 1/2 in (1–2 cm) wider at one end. Use the largest reading: a little extra area costs less than coming up short on the last row.
Area is length × width and the perimeter is 2 × (length + width). If you measure in feet and inches, convert the inches to decimal feet before multiplying (6 in = 0.5 ft, 3 in = 0.25 ft), or enter the numbers straight into the floor renovation calculator, which accepts feet, inches and fractions.
L- and U-shaped rooms
There are two ways to measure a room that isn’t a rectangle. The first is to split it into rectangles, work out each area and add them up. That gives a correct area but a wrong perimeter, because the walls where the rectangles meet get counted even though they don’t exist. The second way, and the more reliable one for baseboard, is to walk the room: start in one corner, measure each wall in turn and note whether you turn left or right at its end.
Walking the walls also checks your own measurements. If the walls you wrote down don’t bring you back to the starting corner, one reading is wrong. The calculator’s L/U-shape mode does exactly this: it rebuilds the outline from your walls, reports if it doesn’t close (and by how much), and counts inside and outside corners for corner pieces.
Example 1 (feet): an L-shaped living room
- Walk the walls from the bottom-left corner: 16 ft, turn left, 12 ft, left, 6 ft, left, 5 ft, turn right, 10 ft, left, 7 ft, left — back at the start.
- Area: the outer rectangle is 16 × 12 = 192 sq ft; the missing corner is 10 × 5 = 50 sq ft; 192 − 50 = 142 sq ft.
- Perimeter: 16 + 12 + 6 + 5 + 10 + 7 = 56 ft.
- Corners: five left turns are inside corners and one right turn is an outside corner.
- Baseboard: 56 ft minus one 32 in doorway (2.67 ft) = 53.33 ft; with 10% for cuts that is 58.67 ft, so eight 8 ft pieces.
Splitting the same room into a 16 × 7 ft and a 6 × 5 ft rectangle gives the same 142 sq ft, but adding up both rectangles’ perimeters gives 68 ft of “walls” — 12 ft of baseboard you would never install.
Closets, alcoves and what to leave out
Closets and alcoves that get the same floor are part of the room: add them as extra rectangles. Anything that stays in place and won’t have flooring under it should be subtracted: a kitchen island, a bathtub, a shower base, a built-in wardrobe. Floating floors must not be pinned under heavy fixed cabinets anyway, so laminate and click vinyl usually stop at the island and get trim around it.
For each exclusion, decide whether it gets baseboard around it. An island with a toe kick usually doesn’t; a freestanding pillar does. In the calculator that is the “needs baseboard around it” switch on each exclusion.
Example 2 (meters): a bedroom with a built-in wardrobe
- Room 4.2 × 3.6 m = 15.12 m²; perimeter 2 × (4.2 + 3.6) = 15.6 m.
- Built-in wardrobe 1.2 × 0.6 m = 0.72 m², excluded and not skirted: net area 15.12 − 0.72 = 14.40 m².
- One 0.8 m doorway: skirting length 15.6 − 0.8 = 14.8 m.
- With 10% for cuts: 16.28 m → seven 2.4 m boards (16.8 m), 0.52 m left over.
Doorways and thresholds
Measure each doorway between the jambs. Baseboard stops at the door casing, so the door width comes off the baseboard length. Each doorway also needs a transition strip where the new floor meets the next room, and two end caps if your baseboard uses them. Decide now where the floor ends: usually under the door, in line with the door leaf when it is closed.
Common measuring mistakes
| Mistake | What happens | Fix |
|---|---|---|
| Measuring at waist height | Cabinets and baseboard shorten the reading | Measure at floor level, wall to wall |
| One reading per wall | Out-of-square rooms come up short | Measure both ends and the middle, use the largest |
| Adding rectangle perimeters | Baseboard is overestimated | Walk the walls instead |
| Forgetting closets | Last box or bag is missing | Add every alcove as its own area |
| Mixing inches and decimal feet | 10 ft 6 in entered as 10.6 ft | Convert inches ÷ 12, or let the calculator do it |
Once the room is measured, the next decisions are about waste and packaging. How much extra tile to buy explains the waste allowance for each layout, and the tile calculator or laminate calculator turns your measurements into whole boxes.
Frequently asked questions
Should I measure in feet or inches?
Either works as long as you don’t mix them. Measure to the nearest 1/4 in and convert to decimal feet (inches ÷ 12) before multiplying, or enter feet and inches directly into the calculator.
Do I subtract the area under kitchen cabinets?
Yes, if the cabinets stay in place. Floating floors should not be installed under heavy fixed cabinets, and tile under them is usually wasted.
How do I measure a room with an angled wall?
Split it into a rectangle and a triangle (half of base × height), or measure the longest length and width and treat the extra as waste. For baseboard, measure the angled wall itself.
Why does the calculator say my walls don’t close?
The walls you entered don’t lead back to the starting corner, usually because one wall was mismeasured or a turn was entered the wrong way. The message tells you how far off it is.