How to measure and size rooms for a floor plan

What to measure, and in what order

Measure what cannot change first: the outside shape of the space, the entry door, the position and width of each window, and any column, chimney or pipe in the room. Those facts decide where everything else can go.

Then measure the flexible spaces wall by wall. For each room you need the internal width and depth, taken at the narrowest point if a wall is not straight. Measure to the face of the finish rather than the skirting, because furniture goes against the wall.

Finally, note the heights that matter for the room's use. A low ceiling changes what a room can hold, and a ceiling height of 2400 mm says more about a bedroom than its area does. The builder stores two dimensions per room, so keep the heights in your notes rather than forcing them into the plan.

• Outside shape, entry door, windows and fixed obstacles first
• Internal width and depth of each room, wall by wall
• Measure to the finish face, not to the skirting
• Keep ceiling heights and clearances in your own notes

Note: A single measurement error propagates. A wall that is 50 mm out shifts every room that touches it, so re-measure the corners before you commit the number.

Work in millimeters and write it down

Millimeters suit this work. A tape measure reads in millimeters, and a plan drawn in millimeters has no conversion step between the wall and the number you type. Metres with two decimals lose precision exactly where you need it, and feet with fractions are worse.

Write each measurement down as you take it, with the room name beside it. Six lines like "kitchen 4000 wide, 3200 deep, window on north wall 1200" are enough to rebuild the room later, and they take less time than walking back with a phone.

Then record where you measured from. "Kitchen 4000 by 3200" is ambiguous the moment you come back to it; "kitchen 4000 by 3200, measured along the window wall, 300 from the corner to the door frame" is not. Canvasola stores geometry in millimeters as integers, so a clean number in the notes becomes a clean number in the plan.

• Millimeters match the tape measure and the stored geometry
• Write the measurement and the room name in the same line
• Record where you measured from, not only how far
• Keep the list next to the builder while you type it in

Type the sizes into the inspector

Dragging a rectangle to the right size is guesswork, and a guess is how a plan starts to lie. Select a room, open the inspector, and type the real width and height into the Width (mm) and Height (mm) fields. The rectangle resizes to match and the area label recalculates at once.

The same rule applies to everything else that carries a number. A wall has a Length (mm) and a Thickness (mm). An opening has a Width (mm) and a Position along wall (mm). A dimension line has a Length (mm) you can set exactly and a Label offset (mm) that moves the text clear of the wall.

When a number is close but not exact, two controls help. The Grid setting in the inspector offers a 500 mm option, a 50 mm fine grid and Off, and the 50 mm fine grid suits work that has to be exact. A nudge with the arrow keys moves the selection by 10 mm, and Shift makes the step 50 mm. The rest of the app's shortcuts are in the keyboard shortcut cheat sheet.

1. Select the room. Use the Select tool and click the room, or press Tab to move between the entities on the plan.
2. Type the dimensions. Enter the measured width and height in millimeters in the inspector and watch the area label follow.
3. Fine-tune with the arrow keys. Nudge by 10 mm with an arrow key, or by 50 mm when you hold Shift, and read the label again.

Note: A typed number is only as good as the measurement behind it, so the inspector cannot tell an estimate from a tape measure. Say which is which in a note on the plan.

Let the area follow the geometry

The area is never typed in here. It is calculated from the room rectangle every time the geometry changes, and rounded only for display: one decimal place in square meters, whole square feet in imperial. That is why the area and the shape can never disagree.

The same rule governs the rest of the plan. Lengths come from the walls rather than sitting next to them, so editing a wall updates every dimension line attached to it. One source of truth per measurement is what makes a plan worth checking.

There is one useful consequence. If a room area looks wrong, the geometry is wrong, and you can find it in one move by comparing the room against the dimension lines you drew for it. The pillar guide shows the order of work that keeps a plan consistent from the first rectangle onward.

• Area is calculated from the rectangle, never typed in
• Areas round for display only: 0.1 m² and whole ft²
• Lengths come from the walls, so edits propagate
• A wrong area means wrong geometry, not a wrong number

Switch units without changing a single number

The Units control in the inspector switches between Metric (m) and Imperial (ft-in), and it is purely a display choice. The geometry stays in millimeters inside the document, so switching units never alters a stored value, never re-rounds an area and never shifts a wall by a fraction of a millimeter. You can switch back and forth as often as you like.

Imperial shows feet and whole inches rather than a decimal foot, because a decimal foot is a number nobody can measure with. A room of 4.00 by 3.60 meters reads 14.4 m² in metric and 155 ft² in imperial.

Set the units to the system your reader uses before you export, rather than sending a file that mixes the two. The room schedule CSV carries both systems in separate columns, so a spreadsheet can hold the metric figure and the imperial figure side by side without anyone converting anything by hand.

• Metric (m) and Imperial (ft-in) are display preferences only
• Imperial shows feet and whole inches, never a decimal foot
• Set the unit system before you export, not after
• The CSV schedule carries both systems in separate columns

Check the sizes against how the room is used

A correct measurement can still be the wrong plan. A bedroom of 12 m² with a 3.6 m ceiling is generous; the same 12 m² with a low ceiling and a door in the corner is not. Test each room against its use the way you would on a real visit: can two people work here, does the bed still let the door open.

Then compare the plan against the total. The room schedule ends with a total area, and the sum of the rooms should match the floor area you measured. If it does not, the difference is usually a corridor or a wall that you have not drawn as a room yet, which is worth knowing before you send the plan to anyone.

Finally, write down the source of every number. A plan drawn from your own tape measure and one drawn from a catalog are different documents, even when the areas look similar, and the difference matters when somebody asks where the figures came from.

• Test each room against the use, not against its area alone
• Compare the schedule total with the floor area you measured
• Account for any gap, such as a corridor not yet drawn
• Record the source of every measurement you used

Note: An area is a rectangle, so it says nothing about how a space feels. Check the shape and the ceiling as well as the number.

A checklist you can reuse

• Fixed obstacles, doors and windows were measured first
• Every measurement is written down in millimeters
• Width and height were typed into the inspector, not dragged
• Nudges of 10 mm and 50 mm were used for fine adjustments
• Room areas were read from the label, never entered by hand
• Units were switched to the reader's system before exporting
• The schedule total was compared with the measured floor area

Common mistakes to avoid

• Dragging rooms to the right size. A dragged rectangle is an estimate, and the estimate ends up inside an area label that looks authoritative. Type the measured width and height instead.
• Measuring to the skirting board. Furniture sits against the wall finish, not against the timber trim. Measure to the finished face, or every room will be a few millimeters optimistic.
• Mixing units while measuring. Half a number converted into feet and inches is a number nobody can check twice. Measure everything in millimeters and convert once at the end.
• Believing a template area as a measurement. Catalog dimensions are typical examples rounded to 50 mm. They are a starting point for comparison, never a substitute for your own tape measure.
• Treating the area as the whole story. Area says nothing about ceiling height, shape or door position. Test each room against the use you have in mind before you trust the number.

Frequently asked questions

Why does the builder use millimeters instead of meters?

Because millimeters are what a tape measure reads, and because storing whole millimeters keeps the geometry exact. A wall drawn at 3600 mm is stored as 3600, so there is no rounding drift in the dimension arithmetic and no half-millimeter offsets to explain later.

Can I switch to feet and inches for a client in the United States?

Yes, and it changes nothing underneath. Choose Imperial (ft-in) in the inspector and the labels, the dimension lines and the room schedule switch over, while the stored geometry stays in millimeters exactly as it was. Switching back and forth as often as you like is safe.

What if I do not know the exact size of a room?

Type an estimate and mark it as an estimate in a note on the plan. The label will move as you refine the number, and the note keeps you and everyone else honest about which figures are measurements and which are assumptions.

Can the builder measure a room for me?

No. It has no camera, no measuring tool and no import from a laser meter. You supply the dimensions and the builder keeps them exact, recalculates the areas from the geometry, and keeps them consistent when the shape changes in the plan.

This guide is part of the floor plan guides collection. For the wider product tour, read the complete Canvasola guide, and keep the keyboard shortcut cheat sheet open while you work.