HO Code 83 vs Code 100
Code 83 and Code 100 are the two rail sizes you meet most in HO. They are the same gauge, so the same trains run on both, but the rail itself is a different height: Code 100 stands 0.017 in (0.43 mm) taller. This page sorts the HO lines from Atlas, Kato and Bachmann into the two sizes, each with its maker's page, and sets out what the makers list for joining one to the other. Atlas sells both sizes as Snap-Track sectional pieces and Super-Flex flexible track; the two Atlas Snap-Track rows below give the ties, the flex item and the curve radii for each size.
What the Code number measures
Kato's UNITRACK catalog explains that the Code number is the rail height in thousandths of an inch: its HO rail is Code 83 because the rail is 0.083 in. (2.11 mm) tall.
Kato UNITRACK catalog (PDF), p. 27 · verified 2026-09-26| Rail code | Rail height | HO lines in this size |
|---|---|---|
| Code 83 | 0.083 in · 2.11 mm | 3 |
| Code 100 | 0.100 in · 2.54 mm | 2 |
| Difference | 0.017 in · 0.43 mm | — |
Heights in italics, and the Code 100 row as a whole, are our arithmetic from the Code rule above (1 in = 25.4 mm). Only the Code 83 figure, 2.11 mm, is printed by a maker, in Kato's catalog.
Which HO lines are which
6 HO lines · 3 Code 83 · 2 Code 100 · 1 with no Code number printed. Sorted from the table below — see method. Curve radii come from the curve radius page.
Code 83
| Line | Ties and roadbed | Flexible track | Curve radii listed |
|---|---|---|---|
| Atlas HO Code 83 track (Snap-Track, Super-Flex) Atlas page · verified 2026-09-26 | Brown ties, nickel silver rail source · verified 2026-09-26 | Super-Flex, item 0500, 36 in. per piece source · verified 2026-09-26 | 15", 18", 22", 24" |
| Atlas HO Code 83 True-Track (track with roadbed) Atlas page · verified 2026-09-25 | Gray ballasted roadbed; the Code 83 Snap-Track on it can be removed and used on its own source · verified 2026-09-26 | none in this line The True-Track listing we checked is all sectional pieces. Atlas's Code 83 Super-Flex (row above) has the same rail code. source · verified 2026-09-26 | 18", 22", 24" |
| Kato USA HO UNITRACK (track with roadbed) Kato UNITRACK catalog (PDF), p. 27 · verified 2026-09-26 | One-piece molded gray plastic roadbed source · verified 2026-09-25 | HO Concrete Tie Flexible Track, item 2-001, 900 mm per piece Kato's catalog doesn't give this piece its own Code number. It says that laid on Kato's HO cork roadbed (item 6-010), its rail comes out level with HO UNITRACK. Kato UNITRACK catalog (PDF), p. 33 · verified 2026-09-26 | R370, R430, R490, R550, R610, R670, R730, R790, R1546, R1606 |
Code 100
| Line | Ties and roadbed | Flexible track | Curve radii listed |
|---|---|---|---|
| Atlas HO Code 100 track (Snap-Track, Super-Flex) Atlas page · verified 2026-09-26 | Black plastic ties, nickel silver rail source · verified 2026-09-26 | Super-Flex, item 0168, about 3 ft per piece source · verified 2026-09-26 | 15", 18", 22", 24" |
| Bachmann HO Flex Track (item 44371) Bachmann page · verified 2026-09-25 | Black ABS plastic ties with a wood-grain finish, nickel silver rail source · verified 2026-09-25 | Flex Track, item 44371, 36 in. per piece source · verified 2026-09-25 | flexible track only |
No Code number printed
Bachmann HO E-Z Track, nickel silver with gray roadbed
no Code number on the maker pages we checked. Bachmann's page describes the rail as nickel silver but prints no Code number, and its Code 100 Flex Track is a separate line, so it can't stand in for this one.
Bachmann page · verified 2026-09-25Joining Code 83 to Code 100
Because the rail tops differ by 0.43 mm, a plain rail joiner between the two sizes leaves a step. Here is what the makers themselves list for bridging it:
Atlas item 0551, HO Code-83 Transition Joiners
Atlas lists an HO Code-83 Transition Joiners product, item 0551. The product page shows only the name and item number. Its description and specification tabs are empty, so the page itself doesn't say which two rail sizes the joiner is for.
Atlas product page · verified 2026-09-25Transition track sections
None found. None of the Atlas HO pages we checked (Code 100 track, Code 100 and Code 83 Snap-Track, True-Track) lists a length of transition track between Code 83 and Code 100.
verified 2026-09-26For comparison: Atlas N scale
In N scale, Atlas does sell transition track between its own rail codes, e.g. item 2590, described as Code 65 to Code 80. Atlas does make this kind of part; we just didn't find an HO Code 83 to Code 100 version.
Atlas product page · verified 2026-09-25Kato's UNITRACK catalog lists no transition track to other makers' rail. That check, and the cross-brand picture for Kato, Atlas and Bachmann together, is on the track interchange page.
Known gaps
- Atlas's HO Code 100 and Code 83 pages don't print the rail height itself. The heights on this page come from the Code-number rule as Kato's catalog explains it (Code 83 = 0.083 in.), applied to both codes; the Code 100 height and the difference between the two are our arithmetic.
- The item 0551 transition joiner page has no description, so this page doesn't say what it joins or how it is used.
- Bachmann doesn't print a Code number for E-Z Track, so it isn't placed in either column. It is not a Code 83 or Code 100 verdict.
- Tie spacing, tie height and roadbed height are not published on these pages, so the page compares rail code only. Two lines with the same code can still sit at different heights once roadbed is counted.