OO Scale to HO Scale Conversion
To convert a model dimension from OO Scale (1:76) to HO Scale (1:87), multiply it by 0.8736 (76 ÷ 87). The result is a smaller model — every length, width, and height changes by the same factor.
Conversion Chart
| OO Scale size (mm) | HO Scale size (mm) |
|---|---|
| 1 mm | 0.87 mm |
| 2 mm | 1.75 mm |
| 5 mm | 4.37 mm |
| 10 mm | 8.74 mm |
| 20 mm | 17.47 mm |
| 50 mm | 43.68 mm |
| 100 mm | 87.36 mm |
Frequently Asked Questions
How do I convert OO Scale to HO Scale?
Multiply any OO Scale model dimension by 0.8736 to get the HO Scale dimension. This works because OO Scale is 1:76 and HO Scale is 1:87, so the factor is 76 ÷ 87 = 0.8736.
Is HO Scale bigger or smaller than OO Scale?
HO Scale models are smaller: the same subject is only 0.8736× the size in each dimension compared to OO Scale.
Keep Exploring
Reverse: HO Scale to OO Scale · OO Scale (1:76) guide · HO Scale (1:87) guide · Full calculator