CYCLE CALCULATORS

CalculatorsOptimal Chain Length Calculator

Optimal Chain Length Calculator

A new chain is sized on the big-big combination, then you never ride big-big. This uses the standard link formula and rounds up to an even number so a quick link can close it.

Inputs

Units

Results

Chain links
110

The Result is indicative and educational. It does not constitute a design, a technical opinion or medical advice and does not replace calculations or verification by a person with the appropriate qualifications and authorisations. Before purchase, installation or use in practice – in particular in electrical installations – the Result should be verified by a qualified specialist. Details: Terms of Service, point 4.

How the number is made

The inch equation is L = 2 × chainstay-in-inches + largest ring ÷ 4 + largest cog ÷ 4 + 1. Pitch is half an inch, so links = 2 × (chainstay mm ÷ 12.7) + (ring + cog) ÷ 2 + take-up. Take-up is 2 links, or 4 links when the largest cog is 42 T or bigger (Park Tool’s extra slack for a long-cage clutch). Round up to the next even number so a quick link can close.

This bypasses the derailleur, the same way you size on the stand. On full suspension, let the air out of the shock and size at the point in the travel where the rear axle sits farthest from the bottom bracket. Do not cut until the chain wraps the big ring and big cog by hand. An odd count cannot close on a master link.

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Questions

Why an even number?

A master link joins inner to outer. An odd count leaves two outers or two inners facing each other.

Do I wrap big-big to check?

Yes. The formula gets you close. Wrap big ring and big cog with the derailleur out of the path, then keep the take-up (two links, or four if the cog is 42 T or bigger) before you cut.

When does the chain gain two extra links?

The usual take-up is two links. A largest cog of 42 teeth or more adds two further links, the allowance for a dedicated 1x. Park Tool writes the two-link rule for cogs up to 36 T and the four-link rule from 42 T; for 37–41 T this calculator keeps two links, so confirm the wrap on the bike.

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