Scale Converter
Converts between a scale ratio (such as 1:100) and real-world or model dimensions, working out the scaled length or the actual size.
Enter Values
Minimum 0
Minimum 0
Minimum 0
How to use this calculator
- Enter the scale (the N in 1:N).
- Enter either the real size or the model size to get the other.
How it works
Model size = real size ÷ scale; real size = model size × scale. Both use the same unit.
Worked example
1:87 (HO), real 4350 mm. Model size = 50 mm.
Common mistakes
- Mixing units between the real and model figures — keep both the same.
- Entering the scale as a ratio (1:87) instead of just the number (87).
Frequently asked questions
How do scale ratios work?
A scale like 1:100 means one unit on the drawing equals 100 units in real life, so 1 cm represents 1 m.
How do I convert a real measurement to scale?
Divide the real length by the scale factor; at 1:50, a 5 m wall is drawn 5 ÷ 50 = 0.1 m, or 10 cm.
What does 1:87 mean?
The model is 1/87th of the real object — 87 mm in real life becomes 1 mm on the model.
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Cite this tool
Zerdly. (2026). Scale Converter. Retrieved from https://www.zerdly.com/tools/scale-converter/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.