How to Use the Roller Chain Length Calculator
When two sprockets are connected by a roller chain, the required number of links is fully determined once you know the teeth counts and center distance. Unlike a belt, a chain can only close with a whole number of links â cut one by eye without calculating first, and you often end up needing a weaker offset link to make an odd link count work.
This calculator uses the standard roller chain design formula: link count = 2C/p + (N1+N2)/2 + p(N2-N1)Âē/(4ÏÂēC), where C is center distance, p is chain pitch, and N1/N2 are the small and large sprocket teeth counts. The result is always rounded up to the next even number so the chain closes without an offset link, and that even link count is multiplied by pitch to give the actual chain length.
Chain pitch sizes use the standard ANSI roller chain numbering (#25 through #100) â the same standard used worldwide for this chain type. In practice, installers often nudge the center distance slightly to match the rounded chain length, or use a chain tensioner to absorb the small amount of slack.
Frequently Asked Questions
Roller chains assembled with an odd number of links need an offset link, which is weaker and more expensive. Rounding the calculated link count up to the next even number lets the chain close without an offset link.
Yes, slightly. In practice you either widen the center distance a bit to match the rounded chain length, or use a chain tensioner to take up the small amount of slack.