BS to ANSI chain cross-reference
Same pitch does not mean same chain. This chart pairs British and American standard sizes, and flags where they are not interchangeable.
Pitch equivalents & the roller trap
Chains are paired by pitch below. The roller diameter is what decides whether a swap is safe. Fitting the wrong roller wears sprocket teeth into hooks.
| Pitch | Pitch (mm) | British Standard | ANSI | ANSI roller Ø (mm) | Interchangeable? |
|---|---|---|---|---|---|
| 1/4" | 6.35 | — | 25 | 3.30 | — |
| 3/8" | 9.525 | 06B (6.35 roller) | 35 | 5.08 | Different rollers, not interchangeable |
| 1/2" | 12.70 | 08B (8.51 roller) | 40 | 7.92 | Same pitch, different roller Ø. Check before fitting |
| 5/8" | 15.875 | 10B (10.16 roller) | 50 | 10.16 | Rollers match; plate dimensions differ |
| 3/4" | 19.05 | 12B (12.07 roller) | 60 | 11.91 | Same pitch, different roller Ø |
| 1" | 25.40 | 16B (15.88 roller) | 80 | 15.88 | Rollers match; plate dimensions differ |
| 1 1/4" | 31.75 | 20B (19.05 roller) | 100 | 19.05 | Rollers match; plate dimensions differ |
| 1 1/2" | 38.10 | 24B (25.40 roller) | 120 | 22.23 | Different rollers, not interchangeable |
| 1 3/4" | 44.45 | 28B | 140 | 25.40 | Check both dimensions |
| 2" | 50.80 | 32B | 160 | 28.58 | Check both dimensions |
Roller diameters shown for the ANSI chain; BS roller diameters are given in brackets in the BS column. Full dimensions on the BS and ANSI range pages. Unsure what you have? How to identify a roller chain.
Straight answers
Is 08B the same as ANSI 40?
No. Both have a 12.70 mm (1/2 inch) pitch, but 08B has an 8.51 mm roller and ANSI 40 has a 7.92 mm roller. They are not interchangeable, and fitting the wrong one damages sprockets.
Which BS chain matches ANSI 60?
ANSI 60 and BS 12B share a 19.05 mm (3/4 inch) pitch, but their roller diameters differ (11.91 mm vs 12.07 mm). Match the roller and plate dimensions, not just the pitch.
How do I tell BS from ANSI chain?
Measure the pitch first, then the roller diameter; the roller usually settles it. Where rollers match, plate height and thickness differ. Send us a photo with a rule and we will confirm it.
Still not sure which you've got?
Send a photo next to a rule. We identify chains every day, and we'll tell you if a cheaper standard part does the job.