Chain Length Calculator
Enter both sprocket tooth counts, center distance and chain pitch to get the exact chain length — rounded to an even link count to avoid offset links.
Open calculatorLast updated: 2026-09-15
How the calculation works
- The classical chain equation wraps straight spans plus arc contact on each sprocket, expressed in pitches.
- The result rounds UP to the nearest even pitch count — even counts use a standard connecting link instead of a weaker offset link.
- Pitch conversions for ANSI sizes (#25–#60) are built in.
Worked example
Interpreting the result
Chain drives wear by pitch elongation: a 'stretched' chain rides higher on sprocket teeth and eventually jumps. Order two links extra with a tensioner, or set center distance adjustable by ±2 pitches. Never reuse an offset link in a power drive — it's the weak point.
Assumptions
- Standard roller chain, two-sprocket drive, no idlers.
- Slight chain tension at installation.
Limitations
- Idler sprockets and serpentine paths add length segments — measure those separately.
- Chain sag in long horizontal spans needs a catenary allowance.
Chain links needed for a 12.7 mm (1/2 in) pitch chain
| Sprockets (small / large) | 300 mm centres | 400 mm centres | 600 mm centres |
|---|---|---|---|
| 17 / 34 teeth | 74 | 90 | 122 |
| 15 / 45 teeth | 80 | 94 | 126 |
| 19 / 38 teeth | 78 | 92 | 124 |
Rounded up to an even number of links so no offset link is needed.
Worked scenario: 17 and 34 teeth on 400 mm centres
The theoretical length is 88.72 pitches, which rounds to 90 links, a chain about 1,143 mm (45 in) long. After rounding, the centre distance is adjusted slightly to suit the real chain.
Mistakes to avoid
- Rounding to an odd number of links, which needs a weaker offset link.
- Leaving no way to adjust the centre distance or tension the chain.
- Mixing up the chain pitch with the roller diameter. Pitch is the distance between pins.
Frequently asked questions
How do I measure chain pitch?
Center-to-center distance of three consecutive pins, divided by two. 12.7 mm = #40 chain.
Why even number of links?
An even count closes with a spring-clip connecting link (full strength). Odd counts need an offset link — two pins on a bent side plate, roughly 20–30% weaker.