A scale of 1:N means one unit on the drawing or model equals N of the same unit in reality. On a 1:50 drawing, 1 cm represents 50 cm; on an HO-scale (1:87) model railway, a 15 m locomotive is about 17 cm long.
How to use the Scale Calculator
- Scale
- Custom scale 1 :
- Real length
- Every result field is editable: type into Scaled length and Real length plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
The real length is divided by N to give the scaled length. Type a scaled measurement into the result to get the real-world size.
Inputs explained
| Field | What to enter |
|---|---|
| Scale | Choose one: 1:12 (dollhouse), 1:24, 1:32, 1:48 (O scale, ¼″ = 1′) … |
| Custom scale 1 : | A number |
| Real length | Units: m, km, cm, mm, in, ft … |
Example values
How the main result changes when Real length changes and everything else stays at the example values above:
| Real length (m) | Scaled length (cm) |
|---|---|
| 7.5 | 8.6108 |
| 11.25 | 12.9162 |
| 15 | 17.2216 |
| 18.75 | 21.527 |
| 22.5 | 25.8324 |
| 30 | 34.4432 |
Formula
scaled length = real length ÷ N (for a 1:N scale)Worked example
Inputs — Scale: 1:87 (HO scale); Custom scale 1 :: 25; Real length: 15 m.
Results — Scaled length = 17.2216 cm.
Frequently asked questions
What does 1:100 mean?
1 cm on the drawing is 100 cm (1 m) in reality.
How long is a 6 ft person in 1:24 scale?
3 inches.
What is HO scale?
1:87.1, the most popular model railway scale.
What formula does the Scale Calculator use?
scaled length = real length ÷ N (for a 1:N scale).