Model Train Scale Converter
Convert real-world measurements to any model train scale and back.
Works for HO, N, O, Z, G, 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.