Motorcycle Chain Length Calculator
Calculate the number of chain links a motorcycle needs from the front and rear sprocket sizes, center distance and chain pitch.
How it works
Links ≈ (2C ÷ p) + (F + R) ÷ 2 + p × (R − F)² ÷ (4π²C), rounded UP to an even number · C = center distance, p = pitch, F/R = front/rear sprocket teeth
Chain length wraps around both sprockets plus the two straight runs between them, which the standard formula captures from the tooth counts, center distance and pitch. Chains come in whole links and are almost always cut to an even number so a standard connecting link joins the two ends, so the result is rounded up. Because chains only shorten (by removing links) and stretch slightly in service, it is safer to have the adjusters near the middle of their travel — verify the final fit against your swingarm’s adjustment range.
Worked example
With a 15-tooth front, 45-tooth rear, 580 mm center distance and 520-chain pitch of 15.875 mm: 2 × 580 ÷ 15.875 ≈ 73.1, plus (15 + 45) ÷ 2 = 30, plus a small curvature term of about 0.6, totals ≈ 103.7 links — rounded up to 104 links, roughly 1,651 mm of chain.
Sources: Roller chain — length calculation
Frequently asked questions
Why round chain length to an even number of links?
A standard connecting (master) link joins two "female" ends, which requires an even link count. Odd lengths need a special offset/half link that is weaker and best avoided, so chains are cut to an even number.
What is chain pitch and how do I identify it?
Pitch is the distance between pins — the first digits of the chain size encode it. 415/420/428 chains are ½ inch (12.7 mm), 520/525/530 are ⅝ inch (15.875 mm), and 630 is ¾ inch (19.05 mm). The later digits indicate width, not pitch.
Does changing sprocket sizes change the chain length?
Yes. Larger sprockets or a longer center distance need more links. If you re-gear, recompute the length and check it against your swingarm adjuster range — a bigger rear sprocket often requires adding links or moving the axle forward.
Related calculators
Educational estimate — real-world figures vary with load, temperature, traction, tuning and measurement method.