floor plans
How to measure a room for an accurate floor plan
A step-by-step method for measuring a room: tools, sequence, checking square with diagonals, and recording openings, heights and services.
How do you measure a room for a floor plan?
Sketch the room first, then measure each wall at about waist height with a laser or tape, working clockwise from one corner. Measure both diagonals to check the corners are square, then record every door, window, ceiling height and fixed service such as radiators and sockets, noting each position from the nearest corner.
A floor plan is only as good as the measurements behind it. A wall that is 40 mm shorter than you thought can stop a wardrobe fitting, and an unrecorded radiator can block the only sensible place for a sofa. This guide sets out a method that works for a single room or a whole flat, and that gives you numbers you can trust when you start drawing.
What you need
You do not need specialist equipment, but a few tools make the job faster and more accurate.
- A laser distance measure. It reads long walls and ceiling heights in one go and does not sag. Most consumer models are accurate to within about 2 mm over typical room distances.
- A steel tape, 5 m or 8 m. Better than a laser for short distances, around window reveals, into alcoves and anywhere the laser has no flat surface to hit.
- Squared paper or a clipboard with plain paper. You will draw a rough sketch first and write measurements onto it.
- A pencil and a second colour. Use one colour for wall lengths and another for openings and services, so the sketch stays readable.
- A phone camera. Photograph each wall and every awkward corner. Photos answer questions you did not think to ask on the day.
- A helper, if possible. One person holds the end of the tape while the other reads and writes.
Step 1: sketch before you measure
Walk the room and draw its outline freehand. It does not need to be to scale, but it should show every wall, recess, chimney breast, bay and step in the wall line, plus the positions of doors and windows. Number the walls or label the corners (A, B, C and so on) so each measurement has a clear home on the sketch.
Clear the main walls if you can. Measuring behind furniture leads to guesses, and guesses add up.
Step 2: measure the walls in sequence
Pick a starting corner, usually beside the entrance door, and work clockwise around the room. Measure each wall segment from corner to corner, including the short returns around chimney breasts and alcoves.
- Measure at roughly waist height, about 1 m off the floor. Skirting boards and coving distort readings taken at floor or ceiling level.
- Hold the tape level and taut. On long walls, measure twice and compare.
- Record measurements in millimetres if you work in metric. It avoids decimal mistakes and matches how most drawings are dimensioned.
- Measure the overall length of each wall as well as its segments. If the segments do not add up to the overall figure, one of them is wrong.
Step 3: check the room is square with diagonals
Very few rooms are perfectly rectangular, especially in older buildings. Measuring the two diagonals tells you how far out of square the room is. In a true rectangle both diagonals are equal, and each matches the figure from Pythagoras: the square root of length squared plus width squared.
| Room size (internal) | Expected diagonal | Imperial (approx.) |
|---|---|---|
| 2500 × 3000 mm | 3905 mm | 8 ft 2 in × 9 ft 10 in, diagonal 12 ft 10 in |
| 3000 × 3000 mm | 4243 mm | 9 ft 10 in × 9 ft 10 in, diagonal 13 ft 11 in |
| 3000 × 4000 mm | 5000 mm | 9 ft 10 in × 13 ft 1 in, diagonal 16 ft 5 in |
| 3600 × 4800 mm | 6000 mm | 11 ft 10 in × 15 ft 9 in, diagonal 19 ft 8 in |
| 4000 × 5000 mm | 6403 mm | 13 ft 1 in × 16 ft 5 in, diagonal 21 ft 0 in |
As a guide, if the two diagonals differ by more than about 10 mm, the room is out of square and you should note which corners are not at right angles. That matters for fitted items such as kitchens, built-in wardrobes and floor tiles, which show any error along their edges. For an irregular room, divide it into rectangles and triangles on your sketch and measure a diagonal across each one.
Step 4: record doors and windows
For every opening, record its position as well as its size.
- Measure from the nearest corner to the edge of the opening, then the width of the opening, then the distance on to the next corner. The three figures should add up to the wall length.
- Record the height of the opening, and for windows the sill height from the finished floor.
- Note the depth of the reveal and whether there is an architrave or trim, and how wide it is.
- For doors, note the hinge side and which way the door swings. A door swinging into a room takes up floor space that furniture cannot use.
- For windows, note how they open: casement, sash, tilt-and-turn or fixed. An inward-opening window can clash with a desk or blind.
Standard sizes are a useful check. In the UK, many internal door leaves are 1981 mm (6 ft 6 in) high and 762 mm or 838 mm (2 ft 6 in or 2 ft 9 in) wide, but older houses often have non-standard doors, so measure rather than assume.
Step 5: measure heights
Measure the floor-to-ceiling height in at least two places, ideally in opposite corners and in the centre. Floors and ceilings are rarely perfectly level, and a difference of 20–30 mm across a room is common in older properties. Record the lowest figure, because that is the one that limits tall units.
Also measure anything that drops below the ceiling: beams, bulkheads, boxed-in pipes, sloping ceilings under stairs or in loft rooms. For a sloping ceiling, record the height at the low wall, the height at the high point and the horizontal distance between them.
Step 6: locate services and fixed features
Services are easy to overlook and expensive to move. Mark each one on the sketch with its distance from the nearest corner and its height from the floor.
- Radiators: width, height, depth and the position of the valves.
- Sockets, switches, light points and any data or aerial points.
- Water supplies, waste pipes and the soil stack in kitchens and bathrooms.
- Gas meter, electricity meter, consumer unit and boiler.
- Extractor vents, air bricks and flues.
- Fireplaces and hearths, including hearth depth.
Step 7: write it up the same day
Transfer the sketch into a clean drawing while your memory and photos are fresh. Check that segment lengths add up, that diagonals are recorded, and that every opening has three horizontal figures and a height. If something looks odd, go back and measure again rather than adjusting the number to fit.
A few habits help:
- Write units on the sketch, or state at the top that all figures are in millimetres.
- Circle any measurement you are unsure of and recheck it before ordering anything.
- Keep the original sketch and photos with the project. They are the record of what was actually there.
Putting it into Arcvelle Studio
Once you have the numbers, open Arcvelle Studio and draw the walls with exact lengths, working around the room in the same order you measured. Set each wall's height and thickness, add doors with the correct hinge side and swing, and place windows using your corner-to-opening figures. The room is detected from the walls and its area is shown live, which is a quick check that your dimensions close. If you prefer to work in feet and inches, switch units as described in dimensions and units. If you already have a plan from an estate agent or architect, you can trace over it instead, following trace a plan, and use your own measurements to check it.