Last Updated on April 25, 2017 by Dave Farquhar
Plans in model railroad books and magazines are often in a different scale from your favorite. Having a model railroad scale conversion chart helps.
I’m into O scale and the rest of the world, it usually seems, is not. Dimensions for published plans are almost always sized to HO scale, or even S scale of all things. Of course, after A. C. Gilbert imploded in 1967 and took American Flyer with it, it seemed like the “S” is S scale stood for “scratchbuild,” because building it yourself was the only way you were going to get anything, so I guess that’s fair.
Here’s a cheatsheet you can use to convert measurements from one scale to another.
Assumptions: O scale is 1:48, G scale is 1:22.5. If you use a different measurement for either scale, I’m sorry. This won’t be much use to you.
| G Scale | O Scale | S Scale | OO Scale | HO Scale | TT Scale | N Scale | Z Scale | |
| G Scale | 213% | 284% | 339% | 386% | 533% | 711% | 977% | |
| O Scale | 47% | 133% | 158% | 181% | 250% | 333% | 458% | |
| S Scale | 35% | 75% | 119% | 136% | 188% | 211% | 289% | |
| OO Scale | 30% | 63% | 84% | 115% | 158% | 211% | 289% | |
| HO Scale | 26% | 55% | 73% | 87% | 138% | 184% | 253% | |
| TT Scale | 19% | 40% | 53% | 63% | 73% | 133% | 183% | |
| N Scale | 14% | 30% | 40% | 48% | 54% | 75% | 138% | |
| Z Scale | 10% | 22% | 29% | 35% | 40% | 55% | 73% |
Find your scale in the table along the top. Then scroll down to the desired scale and find out the factor you need to enlarge or reduce. So, if, say, I have HO scale plans I want to enlarge to O scale, I run across the top to HO, then down to O scale, and see that I need to enlarge the plans to 181%. If I have O scale plans I want to reduce to S scale, I run across the top to O and down to S, and see I need to reduce the plans to 75%.
You can also do this if a building you want exists in kit form for a different scale. Measure it. Then do the math based on the chart to figure out what size to build everything for your scale of choice.
Further reading
I hope you find this model railroad scale conversion chart useful.
On a somewhat related note, if you’re unsure what scale something is, here’s how to figure that out before you convert it. You might also find my cross-hobby scale conversion helpful.
David Farquhar is a computer security professional, entrepreneur, and author. He started his career as a part-time computer technician in 1994, worked his way up to system administrator by 1997, and has specialized in vulnerability management since 2013. He invests in real estate on the side and his hobbies include O gauge trains, baseball cards, and retro computers and video games. A University of Missouri graduate, he holds CISSP and Security+ certifications. He lives in St. Louis with his family.
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