HO Scale to OO Scale Conversion
To convert a model dimension from HO Scale (1:87) to OO Scale (1:76), multiply it by 1.1447 (87 ÷ 76). The result is a larger model — every length, width, and height changes by the same factor.
Conversion Chart
| HO Scale size (mm) | OO Scale size (mm) |
|---|---|
| 1 mm | 1.14 mm |
| 2 mm | 2.29 mm |
| 5 mm | 5.72 mm |
| 10 mm | 11.45 mm |
| 20 mm | 22.89 mm |
| 50 mm | 57.24 mm |
| 100 mm | 114.47 mm |
Frequently Asked Questions
How do I convert HO Scale to OO Scale?
Multiply any HO Scale model dimension by 1.1447 to get the OO Scale dimension. This works because HO Scale is 1:87 and OO Scale is 1:76, so the factor is 87 ÷ 76 = 1.1447.
Is OO Scale bigger or smaller than HO Scale?
OO Scale models are larger: the same subject is 1.1447× bigger in every dimension in OO Scale than in HO Scale.
Keep Exploring
Reverse: OO Scale to HO Scale · HO Scale (1:87) guide · OO Scale (1:76) guide · Full calculator