Chain Length Calculator

Work out chain length instantly with clear inputs, formula shown and shareable results.

About Chain Length Calculator

The standard formula is twice the chainstay in inches plus half the teeth on the largest chainring and largest cog, plus one link for derailleur wrap, rounded up to an even number since chain links come in pairs.

Formula

Chain length

links = 2 x chainstay (in) + (chainring teeth)/2 + (largest cog)/2 + 1, rounded to an even number

Worked example

With the default values below, Chain Length Calculator returns Chain links required of 78. Change any input above and every figure here is recalculated in your browser.

Inputs used

Largest chainring teeth: 52 teeth
Largest rear cog teeth: 34 teeth
Chainstay length: 41 cm
Chain pitch: 12.7 mm

Results

Chain links required: 78 links
Chain length: 99.06 cm
Links added for derailleur wrap: 3 links
Base calculation: 76 links

Step by step

1Values used
2Chain length
3Chain links required= 78 links
4Chain length= 99.06 cm
5Links added for derailleur wrap= 3 links
6Base calculation= 76 links

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why must the link count be even?

A chain alternates inner and outer links. An odd count cannot close without a half link, which is only used on single-speed setups.

What if the chain is too short?

Shifting to big-big will destroy the derailleur. Always size for the largest chainring and largest cog even if that combination is not meant to be used.