HO Scale to O Scale Conversion
To convert a model dimension from HO Scale (1:87) to O Scale (1:48), multiply it by 1.8125 (87 ÷ 48). The result is a larger model — every length, width, and height changes by the same factor.
Conversion Chart
| HO Scale size (mm) | O Scale size (mm) |
|---|---|
| 1 mm | 1.81 mm |
| 2 mm | 3.63 mm |
| 5 mm | 9.06 mm |
| 10 mm | 18.13 mm |
| 20 mm | 36.25 mm |
| 50 mm | 90.63 mm |
| 100 mm | 181.25 mm |
Frequently Asked Questions
How do I convert HO Scale to O Scale?
Multiply any HO Scale model dimension by 1.8125 to get the O Scale dimension. This works because HO Scale is 1:87 and O Scale is 1:48, so the factor is 87 ÷ 48 = 1.8125.
Is O Scale bigger or smaller than HO Scale?
O Scale models are larger: the same subject is 1.8125× bigger in every dimension in O Scale than in HO Scale.
Keep Exploring
Reverse: O Scale to HO Scale · HO Scale (1:87) guide · O Scale (1:48) guide · Full calculator