How to draw a floor plan to scale

A floor plan is just the room seen from above, drawn so that everything on it is shrunk by the same amount. That last part is what makes it useful: if the drawing is to scale you can measure things on it and trust the answer. If it is not, it is a sketch, and a sketch will not tell you whether the sofa fits.

The steps

1. Measure the room and write every wall length down in millimetres.
2. Pick a scale that fits the room onto your paper — 1:50 for a room, 1:100 for a whole floor.
3. Draw the walls in order, working round the room in one direction from a fixed starting corner.
4. Check the plan closes: the last wall should land exactly back on the first corner.
5. Add the doors and windows, each measured from the nearest corner.
6. Label every wall with its real measurement, not its drawn length.

Choosing a scale

Scale is written as a ratio: at 1:50, one unit on paper is fifty in the real room, so a 4000 mm wall is drawn 80 mm long. The usual choices are:

• 1:20 — detailed work on one small room, like a bathroom or a kitchen run.
• 1:50 — the default for a single room. A 4 m wall becomes 80 mm, so most rooms fit comfortably on A4.
• 1:100 — a whole floor or a small flat.

Work out the largest dimension first and check it fits your paper before you draw anything. A 6 m room at 1:50 needs 120 mm, which is fine on A4; at 1:20 it needs 300 mm, which is not.

Draw the walls in one direction

Start at one corner and work round the room consistently — always clockwise, or always anticlockwise, but never mixing. Each wall starts where the last one ended. This sounds obvious, and it is the single most common way hand-drawn plans go wrong: it is very easy to measure one wall from the wrong end and mirror half the room without noticing.

Use a set square or graph paper for the right angles. Rooms that look square usually are close enough to draw as square, but if you measured the diagonals and they disagreed, draw the room as it really is rather than as it ought to be.

The plan has to close

When you draw the last wall, it should land exactly on the corner you started from. If there is a gap, one of two things is true: a measurement is wrong, or the room is not the shape you assumed. Either way the plan is telling you something useful, and it is worth going back with the tape rather than fudging the last wall to meet the first.

This is the one job software is genuinely better at. Drawing the room in the planner works exactly the same way — a starting corner and then a chain of walls, each with a real length — but the room visibly fails to close if the numbers do not add up, and changing one wall’s length pushes the rest of the chain along instead of leaving a gap.

Symbols worth knowing

• Walls are solid lines, drawn thicker than anything else on the plan.
• Doors break the wall, and are drawn with the leaf open at 90° plus a quarter-circle arc showing the swing. The arc is not decoration — it is how you see which floor the door needs.
• Windows break the wall too, drawn as a thin box across the opening with a line through it.
• Dimensions go outside the room, on the wall they describe.

Label the real measurement

Every wall gets its actual length written on it, not the length it is drawn at. The scale makes the drawing proportional; the labels are what let someone read a number off it without a ruler. State the scale somewhere on the sheet too, and always in millimetres — see how to measure a room for why.

Then add what goes in it

Once the shell is right, furniture is easy: draw each piece as a rectangle at the same scale and move it around. This is where a plan pays for itself, because it is far cheaper to find out on paper that the bed blocks the wardrobe than to find out on delivery day. Standard sizes are in standard door and window sizes.