Floor Plan Scale Calculator
Use the floor plan scale calculator to read real sizes off a scaled plan, work out the scale of an unlabelled drawing from one known dimension, or pick the scale that fits your plan on the paper you can print. It shows metric and imperial scales side by side.
Scale converter
Printing with “fit to page” changes the scale. Print at 100 % (actual size) and check the scale bar with a ruler.
Measured with a ruler, e.g. 42 mm or 4.2 cm
Measured with a ruler, e.g. 42 mm or 4.2 cm
Its length on paper at this scale. Leave blank to skip.
- Real width
- 4.20 m
- 13′ 9″
- Real length
- 3.60 m
- 11′ 10″
- Real floor area
- 15.12 m²
- 162.8 sq ft
- Real length on paper
- 42.0 mm (1.65 in)
At 1:100, a room drawn 42.0 mm × 36.0 mm is 4.20 m (13′ 9″) × 3.60 m (11′ 10″) in reality, and 4.20 m is 42.0 mm on paper.
Opening the room in the Floor Planner
- The editor draws walls on their centre lines. Measure the drawing to the middle of the walls, or add one wall thickness to each inside size, so the room you open matches the plan.
How this was calculated
- Real length = length on the drawing × n (at a scale of 1:n)
- Length on paper = real length ÷ n
- Imperial scales: x″ = 1′ means n = 12 ÷ x (1/4″ = 1′ is 1:48)
- Real width = 42.0 mm × 100 = 4.20 m
- Real length = 36.0 mm × 100 = 3.60 m
- Real floor area = 4.20 m × 3.60 m = 15.12 m²
- Length on paper = 4.20 m ÷ 100 = 42.0 mm
Find the scale of a drawing
Find the scale of a drawing
A bare number is meters; 420 cm and 13' 9" work too
Measured with a ruler, e.g. 42 mm or 4.2 cm
- Scale of the drawing
- 1:50
- Nearest listed scale (within 0.5 %)
- 1:50
The drawing looks like 1:50.
Before you rely on it
- Check against a second dimension before trusting the result: a copy or PDF that was resized changes the scale, and only a scale bar on the sheet stays true.
How this was calculated
- n = real length ÷ length on the drawing; the scale is 1:n
- A listed scale is shown when it is within 0.5 % of n (a ruler reading is rarely closer)
- n = 3.60 m ÷ 72.0 mm = 50.00
Pick a scale that fits the paper
Pick a scale that fits the paper
A bare number is meters; 420 cm and 13' 9" work too
Assumptions
Change any value to match your product or local rules.
Basis: Example only. Your printer and title block decide the margin.
- Smallest n that fits
- 1:32.5
- Suggested listed scale
- 1:50
- Orientation
- Landscape
- Plan size on the sheet
- 240.0 mm (9.45 in) × 180.0 mm (7.09 in)
A plan 12.00 m × 9.00 m fits this sheet (landscape) at 1:50 or any smaller scale.
Other scales
- In imperial scales the same sheet takes 1:48 (1/4″ = 1′).
How this was calculated
- Usable sheet = paper size − 2 × margin, in each direction
- Smallest n = max(plan width ÷ usable width, plan length ÷ usable length), for whichever orientation needs the smaller n
- Suggested scale = the smallest listed 1:n at or above that n
- Usable sheet = 420.0 mm × 297.0 mm − 2 × 10.0 mm = 400.0 mm × 277.0 mm (landscape)
- Smallest n = max(12.00 m ÷ 400.0 mm, 9.00 m ÷ 277.0 mm) = 32.49
- Plan on the sheet = 12.00 m ÷ 50, 9.00 m ÷ 50 = 240.0 mm × 180.0 mm
How scale works
A scale is a ratio
At 1:n, one unit on paper is n of the same unit in reality. Real length = paper length × n; paper length = real length ÷ n.
Imperial scales are ratios too
x″ = 1′ means x inches on paper stand for 12 inches, so n = 12 ÷ x. 1/4″ = 1′ is 1:48 and 1/8″ = 1′ is 1:96.
Finding an unknown scale
Divide a real length you know by the same length measured on the drawing. The result is n.
Fitting a sheet
Take the paper size less the margins, divide the plan’s size by it in each direction and keep the larger figure: that is the smallest n that fits. Round up to a listed scale.
Metric and imperial scales side by side
| Ratio | 1 m in reality on paper | 10 ft in reality on paper | |
|---|---|---|---|
| 1:50 | 1:50 | 20 mm | 61 mm (2.4 in) |
| 1/4″ = 1′ | 1:48 | 20.8 mm | 2.5 in |
| 1:100 | 1:100 | 10 mm | 30.5 mm (1.2 in) |
| 1/8″ = 1′ | 1:96 | 10.4 mm | 1.25 in |
| 1:200 | 1:200 | 5 mm | 15.2 mm (0.6 in) |
| 1/16″ = 1′ | 1:192 | 5.2 mm | 0.63 in |
Worked examples
Drawing to real: at 1:100, a wall 42 mm long on paper is 42 × 100 = 4,200 mm, or 4.2 m. At 1/4″ = 1′ (1:48), 3.5 in on paper is 3.5 × 48 = 168 in, which is 14 ft.
Finding the scale: a wall you know is 3.6 m long measures 72 mm on a plan. 3,600 ÷ 72 = 50, so the plan is at 1:50.
Fitting the paper: a plan 12 × 9 m on A3 landscape (420 × 297 mm) with 10 mm margins leaves 400 × 277 mm. 12,000 ÷ 400 = 30 and 9,000 ÷ 277 ≈ 32.5, so n must be at least 32.5. The next listed metric scale is 1:50, where the plan is 240 × 180 mm on the sheet. In imperial scales the same sheet takes 1/4″ = 1′ (1:48).
Finding the scale of an unlabelled plan
Estate agent plans, old drawings and scans may have no scale, or one that no longer holds because the copy was resized. Pick the longest dimension you can trust: a written dimension on the plan, or a wall you measured yourself. Measure the same line on the paper as precisely as you can and divide. Then check a second dimension. If the two answers disagree by more than a few percent, the plan is probably not drawn to scale and only its written dimensions can be used.
The finder names a listed scale only when your result is within 0.5 % of it, about the accuracy of a careful ruler reading on a typical plan.
Choosing a scale for printing
Choose the largest scale at which the whole plan fits the sheet: larger scales show more detail. Single rooms and furniture layouts read well at 1:50 or 1/4″ = 1′; whole floors of a house may need 1:100 or 1/8″ = 1′ on smaller sheets. Leave room for a title block when you set the margin.
Print at 100 % or “actual size”. “Fit to page” shrinks the drawing and the written scale stops being true; a scale bar on the sheet stays right because it shrinks with the plan. If a printed plan measures wrong, check its scale bar with a ruler: when the bar does not match its labels, the print was resized. The floor plan editor’s PDF export offers 1:50, 1:100 and 1:200 on A4, A3 and US Letter and adds a scale bar to each sheet.
From a scaled drawing to the editor
The converter at the top takes a room’s width and length measured on the drawing and gives its real size. “Design this room” then opens that room in the floor plan editor. The editor draws walls on their centre lines, so measure the drawing to the middle of the walls, or the room will come out one wall thickness smaller than the plan.
Frequently asked questions
How do I convert a measurement using a scale?
Multiply the length on paper by n to get the real length, or divide a real length by n to get its size on paper. At 1:50, 80 mm on paper is 4 m in reality and 3 m in reality is 60 mm on paper.
What does 1:100 mean?
One unit on the drawing stands for 100 of the same unit in reality: 1 mm is 100 mm, 1 cm is 1 m. Areas scale by the square, so 1 cm² on paper is 1 m² in reality.
What is 1/4 inch scale as a ratio?
A quarter inch stands for one foot, which is 12 inches, so 1/4″ = 1′ is 12 ÷ 0.25 = 48, or 1:48. It is close to 1:50 but not the same: over 10 m the difference is about 40 cm.
What is 3/16 inch scale?
3/16″ = 1′ means three-sixteenths of an inch on paper stands for one foot. That is 12 ÷ 3/16 = 12 ÷ 0.1875 = 64, so the ratio is 1:64: 1 inch on the drawing is 64 inches, or 5′ 4″, in reality. Pick 3/16″ = 1′ in the scale list to convert with it.
How do I find the scale of a drawing?
Measure a line on the drawing whose real length you know and divide the real length by the paper length, in the same unit. A 3.6 m wall drawn 72 mm long gives 3,600 ÷ 72 = 50, so 1:50.
Can I use this for map or model scales?
Yes. A map or model scale is the same ratio as a drawing scale: at 1:25,000, 4 cm on the map is 4 × 25,000 = 100,000 cm, or 1 km. Pick “Custom” and enter n, up to 1:100,000. For a model at 1:87, a 10 m building is 10,000 ÷ 87 ≈ 115 mm long.
Ready to plan your space?
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