Model Scale Converter
Convert real sizes to model scale: HO, N, OO, 1:24, 1:72 and more.
About this tool
Choose a common scale or type your own ratio, then convert a real measurement to model size or a model measurement back to real size, in mm, cm, m, inches or feet. A quick-reference line shows how big a person is at that scale.
Understanding model scales
A scale written as 1:87 means every length on the model is 1/87 of the real object. Model railways use named scales: HO (1:87) is the most popular worldwide, OO (1:76.2) dominates in Britain, N (1:160) fits big layouts into small spaces, and Z (1:220) is smaller still. Car kits and die-cast models are commonly 1:24, 1:25, 1:43 and 1:18; aircraft 1:72, 1:48 and 1:144; ships 1:350 and 1:700; and dollhouses 1:12, where an inch represents a foot. To convert, divide the real size by the scale: a 4.5 m car is 51.7 mm long in HO, and a 1.8 m person stands 20.7 mm tall. Multiply to go back: a 100 mm HO model represents 8.7 m. This helps when scratch-building, sizing scenery and buildings, or mixing models from different makers. Honest limits: some names cover more than one ratio (O scale is 1:48 in the US, 1:43.5 in Europe and 1:45 in Japan), and OO models run on HO-gauge track, so track width and model scale don't always match. The map scale calculator and the ratio calculator are related.
Frequently asked questions
What scale is HO?
1:87. One unit on the model represents 87 units in reality.
What is the difference between HO and OO?
OO is 1:76.2 (mostly British models), slightly larger than HO's 1:87, but both run on the same 16.5 mm track.
How tall is a person in N scale?
About 11 mm for a 1.8 m person, at 1:160.
How do I convert a real size to a model size?
Divide the real size by the scale denominator, then convert units: 4,500 mm รท 87 โ 51.7 mm.
Is my data sent anywhere?
No. Everything is calculated in your browser, and nothing is stored or sent.