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What does it take to measure and draw your own floor plan?

A tape measure, an hour per floor, and a fixed routine. Here is exactly which measurements to take, in what order — and what you can skip.

What you actually need

• A tape measure at least 5 m long. A 3 m tape folds up halfway across a living room and gives you wrong readings.
• Or a laser distance meter. This is the one item on the list that genuinely saves time when you are on your own: it measures wall to wall without anyone holding the other end.
• Squared or graph paper, plus a pencil and eraser.
• An app or a sheet of scale paper to draw it up neatly afterwards. In HouseSense you can draw the plan directly on screen — even on an iPhone or iPad without LiDAR.

What you do not need: a Pro phone, CAD software, an architect or a surveyor. If the drawing is going into a case the authorities have to approve, or is meant to settle a boundary, that is a different matter — but for ordering flooring, furnishing, comparing homes or getting contractor quotes, your own measurements are enough, as long as the numbers are correct.

The routine, room by room

1. Sketch the room freehand, without measurements. Just the outline, with whatever notches, alcoves and chimney breasts are there. The sketch does not need to be neat; it needs room for numbers.
2. Measure the two sides on the inside, corner to corner, at floor height. Write it down in centimetres. Measure at floor height, not hip height: skirting boards, out-of-true walls and old brickwork all make a difference.
3. Measure the diagonal. This is the step everyone skips, and it is the one that reveals whether the room is actually square.
4. Measure the wall thickness in a door or window reveal. Typically 10–12 cm for a light partition wall and 25–40 cm for an outer wall in an older brick house — but measure it, do not guess.
5. Measure the openings: the width of every window and door, and the distance from the nearest corner to the edge of the opening. Two numbers per opening is enough.
6. Measure the ceiling height at one point in the room. You will need it later if you want wall areas for painting or a 3D model.

Four measurements per room is the minimum: two sides, a diagonal, and a wall thickness. The rest is detail you can add on top.

The maths, written out

Area: a room measuring 4.12 m × 3.05 m has an area of 4.12 × 3.05 = 12.57 m².

Is the room square? The diagonal of a true rectangle at 4.12 × 3.05 m should be the square root of (4.12² + 3.05²) = the square root of (16.97 + 9.30) = the square root of 26.27 = 5.13 m. If you measure 5.21 m, the room is out of square by 8 cm on the diagonal, and the drawing should show it skewed. Otherwise the cupboard or kitchen run will not fit when it goes in against the wall.

Wall area for painting: the perimeter is 2 × (4.12 + 3.05) = 14.34 m. Multiply by the ceiling height of 2.50 m = 35.85 m². Subtract the openings: a door at 0.90 × 2.05 m = 1.85 m², a window at 1.20 × 1.30 m = 1.56 m². 35.85 − 1.85 − 1.56 = 32.44 m² of wall.

Skirting: the perimeter of 14.34 m minus the door width of 0.90 m = 13.44 m. Add 5–10% for waste when cutting to length.

These four sums are the whole basis of a contractor's quote. If you can do them, you can actually use your own floor plan for something. HouseSense works them out automatically once the rooms are drawn — but the result is the same if you do the maths yourself.

The five mistakes that ruin a home-made floor plan

• Chain measuring. "And then 80 cm more, and then 60 cm more" along a wall lets every small error pile up at the far end. Always measure from the same corner — one zero point per wall.
• Forgotten wall thicknesses. Without them the rooms crowd together, and the sum of the rooms does not match the home's outer dimensions.
• Double-counting shared walls. Draw each room separately and place them side by side, and the shared wall easily gets counted twice. The home grows on its own. In HouseSense the walls of two neighbouring rooms snap together into one shared wall, precisely to prevent this.
• Everything drawn square. Old houses are out of true. Draw what you measured, not what you expected.
• Measurements left off. A drawing without numbers is a sketch. Write the key measurements in, even when the drawing is to scale.

How long does it take?

In an ordinary home of 4–6 rooms, the measuring itself typically takes about an hour per floor, if you work systematically and do not have to go back for forgotten measurements. Drawing it up cleanly — plotting it to scale or entering it into an app — takes 20–40 minutes per floor the first time round.

What makes the time balloon is going back and forth. So: take every measurement in one pass, one room at a time, and write it down on the spot. Never assume you will remember 4.12 from the living room once you are standing in the bathroom.

Scale: 1:50 or 1:100

If you are drawing on paper, pick one fixed scale for the whole drawing. 1:50 means 1 cm on paper is 50 cm in reality — it suits a single floor on an A3 sheet and is easy to measure on. 1:100 means 1 cm is 1 m, and is used for a whole house on an A4 sheet.

A room 4.12 m long becomes 8.24 cm on paper at 1:50, and 4.12 cm at 1:100. Never mix the two scales on the same sheet — it is the surest way to produce a drawing nobody can use for anything.

When is your own floor plan good enough?

It is good enough to furnish by, to buy flooring and paint by, to order a kitchen or curtains by, to get contractor quotes from, and to compare homes with. That covers most needs.

It is not a building drawing. If structural changes are planned, or something load-bearing needs to move, a professional has to be involved — and that kind of work has to be approved by the authorities before it starts. And no matter how carefully you measured: a floor plan can never determine whether a wall is load-bearing. Lines on paper say nothing about what the wall is holding up. That takes a building surveyor or an engineer looking at it on site.

The short version

1. Sketch each floor freehand.
2. Measure per room: two sides, the diagonal, the wall thickness, each opening's width and distance from the corner, the ceiling height.
3. Write everything in centimetres, measure at floor height, always from the same corner.
4. Draw it up at 1:50 or 1:100 — or enter the measurements into an app, where the numbers drive the drawing.
5. Double-check one measurement per floor at the end.