RailCompat
SCOPE HO & N scale · every fact cited + dated · “not published” is shown as unknown, never guessed

Minimum curve radius: HO and N sectional track

Each maker sells its curved sectional track in a fixed set of radii, and names them differently: Kato in millimeters (R370, R550…), Atlas and Bachmann in inches (15", 18"…). This page lists every plain curve radius each line offers, on one scale, so you can see which pieces are close to each other. The smallest piece a maker sells is not the tightest curve a locomotive is rated for — that is a separate statement, and we show it only where the maker itself publishes one.

What the makers say about locomotives

Kato USA UNITRACK HO

Kato states that every Kato HO locomotive and car is designed to run through its R550 (550 mm) curve, the radius it calls the basic HO UNITRACK curve and the one that matches its #4 turnout.

Kato USA UNITRACK catalog (PDF), p. 32 · checked 2026-09-26

Kato's catalog prints its own inch figures next to each radius, and they don't always agree between paragraphs (R370 appears as both 14 9/16 in. and 14 13/16 in.). The inch figures on this page are our own conversion (mm ÷ 25.4), not Kato's.

For every other line on this page the locomotive statement is not found in this batch: the category pages we checked list the curve pieces only. Some individual locomotive product pages print a minimum radius for that one model; check the model's own page before buying track for it.

HO scale: curve radii by line

5 lines · 5 with the full category listing checked · 0 checked in part · 1 with a maker's locomotive statement. Counted by summarizeCurveRows() — see method. Values in italics are our own conversion (1 in = 25.4 mm), not the maker's figure.

LineCurve radii listedSmallest listedLocomotive statement
Kato USA
UNITRACK
  • R370 14.6 in
  • R430 16.9 in
  • R490 19.3 in
  • R550 21.7 in
  • R610 24 in
  • R670 26.4 in
  • R730 28.7 in
  • R790 31.1 in
Kato USA UNITRACK catalog (PDF), p. 32 · checked 2026-09-26
Kato's HO catalog lists these as its 22.5-degree curve pieces. It also lists an R867 10-degree piece, which it describes as a supplement for building a siding off its #6 turnout, so it isn't counted as a separate curve size here.
 R370
Kato positions R370 as the tightest piece in the HO range, meant for layouts small enough to sit on a table, and R430 and R490 as small-layout sizes. It doesn't say which of its models will run on them. PDF p. 32
 R550 — see above
Atlas
Code 83 snap track
  • 15" 381 mm
  • 18" 457 mm
  • 22" 559 mm
  • 24" 610 mm
Atlas category page · checked 2026-09-26
Full-section item numbers 0530 (15"), 0532 (18"), 0535 (22"), 0536 (24"). The category also sells 1/3 and 1/2 sections of the same radii; those are shorter pieces, not extra radii.
 15" not found in this batch
Atlas
Code 100 snap track
  • 15" 381 mm
  • 18" 457 mm
  • 22" 559 mm
  • 24" 610 mm
Atlas category page · checked 2026-09-26
Full-section item numbers 0831 (15"), 0833 (18"), 0836 (22"), 0837 (24"); half and third sections of 15" and 18" are also listed.
 15" not found in this batch
Atlas
True-Track (roadbed track)
  • 18" 457 mm
  • 22" 559 mm
  • 24" 610 mm
Atlas category page · checked 2026-09-26
Item numbers 0460 (18"), 0463 (22"), 0468 (24"). There is no 15" piece in this line.
 18" not found in this batch
Bachmann
E-Z Track, nickel silver
  • 15" 381 mm
  • 18" 457 mm
  • 22" 559 mm
  • 26" 660 mm
  • 28" 711 mm
  • 33.25" 845 mm
  • 35.50" 902 mm
Bachmann category page 1 of 4 · checked 2026-09-26
Page 1 of 4 of the category listing (items 1 to 21 of 69), including concrete-tie and bulk variants of the same radii.
Bachmann category page 2 of 4 · checked 2026-09-26
Page 2 of 4 (items 22 to 42). The 28", 33.25" and 35.50" pieces are sold in 18-degree sections, and 33.25" also in 6- and 12-degree sections; Bachmann writes 35.50".
Bachmann category page 3 of 4 · checked 2026-09-26
Page 3 of 4 (items 43 to 63): no plain curved pieces.
Bachmann category page 4 of 4 · checked 2026-09-26
Page 4 of 4 (items 64 to 69): an 18" auto-reversing curved section, the same radius as page 1.
 15" not found in this batch

HO radius ladder

Every radius above in one list, tightest first. Pieces from different makers that sit close together are still different track — they are not interchangeable curves.

  1. 370 mm 14.6 in Kato USA UNITRACK
  2. 381 mm 15" Atlas Code 83 snap track
  3. 381 mm 15" Atlas Code 100 snap track
  4. 381 mm 15" Bachmann E-Z Track, nickel silver
  5. 430 mm 16.9 in Kato USA UNITRACK
  6. 457 mm 18" Atlas Code 83 snap track
  7. 457 mm 18" Atlas Code 100 snap track
  8. 457 mm 18" Atlas True-Track (roadbed track)
  9. 457 mm 18" Bachmann E-Z Track, nickel silver
  10. 490 mm 19.3 in Kato USA UNITRACK
  11. 550 mm 21.7 in Kato USA UNITRACK
  12. 559 mm 22" Atlas Code 83 snap track
  13. 559 mm 22" Atlas Code 100 snap track
  14. 559 mm 22" Atlas True-Track (roadbed track)
  15. 559 mm 22" Bachmann E-Z Track, nickel silver
  16. 610 mm 24" Atlas Code 83 snap track
  17. 610 mm 24" Atlas Code 100 snap track
  18. 610 mm 24" Atlas True-Track (roadbed track)
  19. 610 mm 24 in Kato USA UNITRACK
  20. 660 mm 26" Bachmann E-Z Track, nickel silver
  21. 670 mm 26.4 in Kato USA UNITRACK
  22. 711 mm 28" Bachmann E-Z Track, nickel silver
  23. 730 mm 28.7 in Kato USA UNITRACK
  24. 790 mm 31.1 in Kato USA UNITRACK
  25. 845 mm 33.25" Bachmann E-Z Track, nickel silver
  26. 902 mm 35.50" Bachmann E-Z Track, nickel silver

N scale: curve radii by line

5 lines · 5 with the full category listing checked · 0 checked in part · 0 with a maker's locomotive statement. Counted by summarizeCurveRows() — see method. Values in italics are our own conversion (1 in = 25.4 mm), not the maker's figure.

LineCurve radii listedSmallest listedLocomotive statement
Kato USA
UNITRACK
  • R117 4.6 in
  • R150 5.9 in
  • R183 7.2 in
  • R216 8.5 in
  • R249 9.8 in
  • R282 11.1 in
  • R315 12.4 in
  • R348 13.7 in
  • R381 15 in
  • R481 18.9 in
  • R718 28.3 in
Kato USA UNITRACK catalog (PDF), p. 15 · checked 2026-09-26
R117, R150 and R183 are sold under the name "Compact Curve Track". A curved deck-girder bridge at R448 is listed on the same page but is a bridge, not a plain track piece, so it is left out.
 R117 not found in this batch
Atlas
Code 80 snap track
  • 9 3/4" 248 mm
  • 11" 279 mm
  • 17" 432 mm
  • 19" 483 mm
Atlas category page · checked 2026-09-26
Item numbers 2510 (9 3/4"), 2520 (11"), 2525 (17"), 2526 (19"); half sections of 9 3/4" and 11" are also listed.
 9 3/4" not found in this batch
Atlas
Code 55 sectional track
  • 10" 254 mm
  • 11.25" 286 mm
  • 12.5" 318 mm
  • 13.75" 349 mm
  • 15" 381 mm
  • 16.25" 413 mm
  • 17.5" 445 mm
  • 18.75" 476 mm
  • 20" 508 mm
  • 21.25" 540 mm
  • 30.609" 777 mm
  • 71" 1803 mm
Atlas category page 1 of 2 · checked 2026-09-26
First page of the category listing (items 2010 to 2021).
Atlas category page 2 of 2 · checked 2026-09-26
Second page of the same category listing (items 2022 to 2031).
 10" not found in this batch
Atlas
True-Track (roadbed track)
  • 11" 279 mm
  • 12.5" 318 mm
  • 14" 356 mm
  • 15.5" 394 mm
Atlas category page · checked 2026-09-26
Item numbers 2410 (11"), 2412 (12.5"), 2414 (14"), 2416 (15.5"); a half section of 11" and 12.5" is also listed.
 11" not found in this batch
Bachmann
E-Z Track
  • 11.25" 286 mm
  • 12.50" 318 mm
  • 14" 356 mm
  • 15.50" 394 mm
  • 17.50" 445 mm
  • 19" 483 mm
Bachmann category page 1 of 3 · checked 2026-09-26
Page 1 of 3 of the category listing (items 1 to 21 of 51); Bachmann writes 12.50", 15.50" and 17.50".
Bachmann category page 2 of 3 · checked 2026-09-26
Page 2 of 3 (items 22 to 42): more variants of radii already on page 1.
Bachmann category page 3 of 3 · checked 2026-09-26
Page 3 of 3 (items 43 to 51): more variants of radii already on page 1.
 11.25" not found in this batch

N radius ladder

Every radius above in one list, tightest first. Pieces from different makers that sit close together are still different track — they are not interchangeable curves.

  1. 117 mm 4.6 in Kato USA UNITRACK
  2. 150 mm 5.9 in Kato USA UNITRACK
  3. 183 mm 7.2 in Kato USA UNITRACK
  4. 216 mm 8.5 in Kato USA UNITRACK
  5. 248 mm 9 3/4" Atlas Code 80 snap track
  6. 249 mm 9.8 in Kato USA UNITRACK
  7. 254 mm 10" Atlas Code 55 sectional track
  8. 279 mm 11" Atlas Code 80 snap track
  9. 279 mm 11" Atlas True-Track (roadbed track)
  10. 282 mm 11.1 in Kato USA UNITRACK
  11. 286 mm 11.25" Atlas Code 55 sectional track
  12. 286 mm 11.25" Bachmann E-Z Track
  13. 315 mm 12.4 in Kato USA UNITRACK
  14. 318 mm 12.5" Atlas Code 55 sectional track
  15. 318 mm 12.5" Atlas True-Track (roadbed track)
  16. 318 mm 12.50" Bachmann E-Z Track
  17. 348 mm 13.7 in Kato USA UNITRACK
  18. 349 mm 13.75" Atlas Code 55 sectional track
  19. 356 mm 14" Atlas True-Track (roadbed track)
  20. 356 mm 14" Bachmann E-Z Track
  21. 381 mm 15" Atlas Code 55 sectional track
  22. 381 mm 15 in Kato USA UNITRACK
  23. 394 mm 15.5" Atlas True-Track (roadbed track)
  24. 394 mm 15.50" Bachmann E-Z Track
  25. 413 mm 16.25" Atlas Code 55 sectional track
  26. 432 mm 17" Atlas Code 80 snap track
  27. 445 mm 17.5" Atlas Code 55 sectional track
  28. 445 mm 17.50" Bachmann E-Z Track
  29. 476 mm 18.75" Atlas Code 55 sectional track
  30. 481 mm 18.9 in Kato USA UNITRACK
  31. 483 mm 19" Atlas Code 80 snap track
  32. 483 mm 19" Bachmann E-Z Track
  33. 508 mm 20" Atlas Code 55 sectional track
  34. 540 mm 21.25" Atlas Code 55 sectional track
  35. 718 mm 28.3 in Kato USA UNITRACK
  36. 777 mm 30.609" Atlas Code 55 sectional track
  37. 1803 mm 71" Atlas Code 55 sectional track

Known gaps in this batch

  • The smallest curve a manufacturer sells is not the same thing as the tightest curve a given locomotive can run on. Only Kato publishes a locomotive statement in the sources checked here, and only for HO.
  • Atlas and Bachmann locomotive product pages sometimes print a minimum radius for that model. This page does not collect those per-model figures yet.
  • Flex track (Atlas Super-Flex, Bachmann flex) can be bent to radii not listed here and is left out of this comparison.
  • Radii are listed as each manufacturer names them. Different manufacturers may measure radius to a slightly different point on the track; none of the sources checked here say which point they use.