Roller chain is identified by its pitch – the distance between the centres of two adjacent pins. Measure it wrong and you will order a chain that will not fit your sprockets. This guide shows the two reliable ways to measure pitch, and how to use the result to identify your chain number.
What pitch actually is
Pitch (P) is the distance between pin centres – not the length of a link, and not the outside width of the chain. Roller chains are made to fixed pitch standards: ANSI chains follow ASME B29.1, while B-series chains follow ISO 606 / BS 228 / DIN 8187.
Method 1 – Measure over multiple pitches (most accurate)
- Lay the chain flat and take up any slack.
- Pick a pin near one end as your starting point and measure to the pin 10 pitches away (count 10 gaps, not 11 pins).
- Divide the measured length by 10 to get the pitch.
- Compare the result with the table below.
Example: if the distance across 10 pitches is 158.75 mm, the pitch is 15.875 mm (5/8″) – an ISO 10A-1 or ANSI 50 chain.
Method 2 – Measure a single pitch (quick check)
Place the jaws of a caliper on the centres of two adjacent pin ends. Because pin ends are rounded, read against the inside faces and confirm the figure on a second pair of pins. For chains under 1/2″ pitch this method is less accurate – use Method 1.
Common pitches
| Pitch (mm) | Pitch (inch) | Typical chain numbers |
|---|---|---|
| 12.700 | 1/2″ | 08B-1 (ISO/BS) / 08A-1, 40 (ANSI) |
| 15.875 | 5/8″ | 10A-1, 50 (ANSI) / 10B-1 (ISO/BS) |
| 19.050 | 3/4″ | 12A-1, 60 (ANSI) / 12B-1 (ISO/BS) |
| 25.400 | 1″ | 16B-1, 16B-2 (ISO/BS) / 80 (ANSI) |
| 31.750 | 1-1/4″ | 20B-1 (ISO/BS) / 100 (ANSI) |
| 38.100 | 1-1/2″ | 24B-1 (ISO/BS) / 120 (ANSI) |
| 50.800 | 2″ | 32B-1 (ISO/BS) / 160 (ANSI) / C2082 double pitch |
| 63.500 | 2-1/2″ | C2102 double pitch conveyor |
| 76.200 | 3″ | C2122 double pitch conveyor |
| 101.600 | 4″ | C2162 double pitch conveyor |
Do not stop at pitch – check two more dimensions
Two chains can share the same pitch and still not interchange. Before ordering, also check:
- Roller diameter – A-series and B-series chains of the same pitch use different rollers. For example, 08B-1 uses an 8.51 mm roller while 08A-1 / 40 uses 7.95 mm.
- Inner width – the space between the inner plates, which must match the sprocket tooth width.
If you are still unsure
Send us a photo of the chain next to a ruler, the measured pitch and the number of teeth on the sprocket. Our engineers will identify the chain and quote the correct replacement – including stainless steel and cut-to-length options.
Request a quote – we reply within one business day.
