The Modeller's Scale Conversion Calculator makes it easy to convert real-world measurements to model dimensions, or model measurements back to their full-size equivalents.
Enter a measurement using familiar imperial or metric units, including yards, feet, inches, fractions, metres, centimetres or millimetres. Measurements can be entered naturally, such as 3 feet 2½ inches, 6 ft 3/4, 2.4 metres or 1250 mm.
Choose a popular modelling scale from the list, or enter your own. The calculator understands common scale names such as O-Gauge, OO, HO and N, as well as ratios such as 1:100, 1/72 or 3:88. A single number is assumed to be a 1:n scale.
By default, the calculator reduces a real-world measurement to its corresponding model size. Select the reverse option when you need to find the full-size measurement represented by a model dimension.
The converted measurement is shown prominently, with equivalent metric and imperial values provided for convenient reference.
Model scales describe the relationship between a model and the full-size original. For example, at 1:100, one unit on the model represents 100 of the same units in the real world. The larger the second number, the smaller the finished model will be.
Popular railway scales include O, OO, HO, TT, N and Z. Other modelling subjects commonly use ratios such as 1:12, 1:24, 1:32, 1:48, 1:72, 1:144 and 1:350.
Scale names are not always universal. For example, O and N can represent slightly different ratios depending on the country or modelling convention. When accuracy matters, it is therefore best to check the actual ratio rather than relying on the scale name alone.