ANSI roller chain sizes
Pitch is the distance from one pin centre to the next, and it is the number that has to match the sprocket. Roller diameter and inner width matter for whether the chain sits in the sprocket teeth correctly.
Tensile strength is the breaking load of a single strand, not the working load. Design to roughly one sixth to one eighth of it for continuous duty.
| Chain no. | Pitch (in) | Roller dia (in) | Inner width (in) | Avg tensile (lb) |
|---|---|---|---|---|
| #25 | 1/4 | 0.130 | 1/8 | 925 |
| #35 | 3/8 | 0.200 | 3/16 | 2,100 |
| #40 | 1/2 | 5/16 | 5/16 | 3,700 |
| #41 | 1/2 | 0.306 | 1/4 | 2,000 |
| #50 | 5/8 | 0.400 | 3/8 | 6,100 |
| #60 | 3/4 | 15/32 | 1/2 | 8,500 |
| #80 | 1 | 5/8 | 5/8 | 14,500 |
| #100 | 1 1/4 | 3/4 | 3/4 | 24,000 |
| #120 | 1 1/2 | 7/8 | 1 | 34,000 |
How chain numbering works
Strip the last digit off the chain number and divide what is left by 8. That is the pitch in inches. #40 becomes 4/8, so half an inch. #100 becomes 10/8, so 1 1/4 inches.
The last digit is the variant: 0 is the standard series, 1 is the lightweight series (which is why #41 is narrower and weaker than #40 despite sharing a pitch), and 5 is rollerless bush chain used on slow conveyor work.
An H suffix means heavy series with thicker side plates, and a suffix of 2 or 3 after a dash means double or triple strand.
ISO metric chain equivalents
British and European chain uses ISO 606 B-series numbers. The pitches match the ANSI sizes closely but the roller diameters and plate thicknesses differ, so a B-series chain will run on an ANSI sprocket only badly and will wear both out.
| ISO | Pitch (mm) | Pitch (in) | Nearest ANSI |
|---|---|---|---|
| 05B | 8.00 | 0.315 | #35 approx |
| 06B | 9.525 | 3/8 | #35 |
| 08B | 12.70 | 1/2 | #40 |
| 10B | 15.875 | 5/8 | #50 |
| 12B | 19.05 | 3/4 | #60 |
| 16B | 25.40 | 1 | #80 |
| 20B | 31.75 | 1 1/4 | #100 |
| 24B | 38.10 | 1 1/2 | #120 |
