Model Railroad ReferenceEverything a model railroader needs, in one place.

Scale Converter

Description

Model railway scales are expressed as a ratio — written 1:N — comparing a model's size to the real, full-size prototype it represents. A scale of 1:87 (HO) means the model is 87 times smaller than the real train; the larger the second number, the smaller the model. This calculator converts any length between real-world dimensions and a model scale, or directly between two model scales — useful for finding a locomotive's real-world length from a model measurement, checking whether N scale and HO scale models are compatible in size, or converting a prototype's published dimensions into a model-scale cutting length.

Scale names aren't always consistent between countries. The US, UK, and continental Europe sometimes define the same name differently: British OO (1:76) is not the same ratio as NMRA's American OO (1:76.2) or true HO (1:87), and "G scale" covers several different ratios (1:32, 1:29, 1:22.5, 1:20.3, and more) depending on the manufacturer and which prototype gauge it represents. Select a standards body above — United States, United Kingdom, or European — to see only the scales relevant to your region.

To convert a length: multiply the input by its scale's ratio to get the real-world size, then divide by the target scale's ratio. Real World (1:1) uses the same formula — it's just a ratio of 1.

Sources

Disclaimer: Scale ratios are generally stable, but always check against your specific manufacturer or national standards body to verify measurements.