How-to

How to measure a room for a floor plan — right the first time

Guides · updated 2026-08-18

A floor plan is only as honest as the measuring session behind it. The good news: a room takes fifteen minutes to measure properly, and the method below catches its own errors before you have drawn a single wall.

What you need

• A tape measure (5m covers most rooms) or a laser measure — lasers shine for long spans and ceiling heights.
• A rough sketch of the room’s outline on paper. Not to scale — it is a place to write numbers.
• Someone to hold the dumb end of the tape, ideally.

The method

1. Sketch the outline first, including every jog, alcove and chimney breast. Walk the perimeter once before measuring anything.
2. Measure wall to wall, at floor level. Skirting boards lean, walls bow; the floor line is where furniture actually stands. Measure the clear interior distance — face of wall to face of wall. These are the numbers that decide what fits.
3. Go around the room in one direction, writing each wall segment on the sketch as you go. Every wall, including the short returns beside a chimney breast or alcove.
4. Locate openings from the nearest corner: distance from corner to door frame, frame width, and which way the door swings. Windows: corner to frame, width, and two heights — sill height and head height.
5. Ceiling height, in two or three spots. Old floors are rarely level; note the lowest number if anything tall is planned.
6. Note the immovables: radiators (width + depth — they eat wall like furniture), sockets, light switches, floor vents, boiler.

Check yourself before you draw

Opposite walls of a rectangular room should measure the same within a centimetre or two. If they do not, one number is wrong — or the room genuinely is not square, which you want to know now. For suspicious rooms, measure both diagonals: equal diagonals mean square corners; unequal means the room is a parallelogram and the plan should be too.

The classic ruins, in order: measuring along the skirting instead of the wall face; forgetting which side a door hinges on; one transposed digit (287 written as 278); and trusting the estate agent’s floor plan, which is marketing, not measurement.

Drawing it up

Put the numbers into a planner that respects them. In The Good Room Planner the wall you draw is the interior face — type the clear distances off your sketch and the room’s usable space is exactly what you measured, regardless of wall thickness. Set your real ceiling height, place the openings at their measured offsets, and the plan is a scale instrument: drop the measure tape on any gap and trust the answer. Then furnish it with real products and "will it fit?" is settled before the checkout.

← All guides