Model Train Scale Converter
Convert real-world dimensions to model train scale and back.
Covers HO (1:87), N (1:160), O (1:48), Z (1:220), G (1:22.5), and any custom scale ratio.
How model train scales work:
Every model train scale is defined by a ratio — the number of real-world units that correspond to one model unit. An HO scale ratio of 1:87 means every 87 inches in the real world equals 1 inch on the model. This applies to everything: locomotive length, building height, car width, and track gauge.
The two conversion formulas:
Model size = Real size ÷ Scale ratio
Real size = Model size × Scale ratio
All major scales at a glance:
| Scale | Ratio | Real 1 foot = | Track gauge |
|---|---|---|---|
| Z | 1:220 | 0.055" model | 6.5mm |
| N | 1:160 | 0.075" model | 9mm |
| TT | 1:120 | 0.1" model | 12mm |
| HO | 1:87 | 0.138" model | 16.5mm |
| OO (British) | 1:76 | 0.158" model | 16.5mm |
| S | 1:64 | 0.188" model | 22.5mm |
| O | 1:48 | 0.25" model | 32mm |
| 1 (1:32) | 1:32 | 0.375" model | 45mm |
| G / Garden | 1:22.5 | 0.533" model | 45mm |
Worked examples:
An EMD SD70ACe locomotive is 74 feet 2 inches long in real life (890 inches):
- In HO (1:87): 890 ÷ 87 = 10.23 inches
- In N (1:160): 890 ÷ 160 = 5.56 inches
- In O (1:48): 890 ÷ 48 = 18.54 inches
A standard 40-foot freight car (480 inches real):
- In HO: 480 ÷ 87 = 5.52 inches
- In N: 480 ÷ 160 = 3.0 inches
Modeling structures:
The same formula applies to buildings, roads, and figures:
- An average person is 5'10" (70 inches) tall
- In HO: 70 ÷ 87 = 0.80 inches (20.3mm) — this is why HO figures are sold as “1:87 scale figures”
- A single-story building at 10 feet ceiling: 120 ÷ 87 = 1.38 inches tall in HO
Mixing scales:
Never mix track gauges — HO trains cannot run on N scale track. However, sometimes modelers deliberately use slightly different figure scales for forced perspective (larger figures in the foreground, smaller in background) to make layouts appear deeper than they are.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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