Motorcycle Sprocket & Chain Length Calculator

Method and units

Let C be center distance divided by chain pitch, and T1/T2 be sprocket teeth. Approximate continuous geometry pitch count L = 2C + (T1 + T2)/2 + ((T2 − T1)/(2π))²/C. The page rounds up to a whole pitch only to show a planning length; this is not a ready-to-buy fitment result.

Worked example

For 15/45 teeth, 520 pitch (15.875 mm) and 600 mm center distance, the continuous geometry estimate is about 106.2 pitches; rounding up for planning gives 107 pitches (about 1,698.6 mm of pitch length), not a ready-to-buy chain length.

Supported inputs and interpretation

Teeth are integers: front 8–40, rear 8–100; pitch 5–25 mm; center distance 100–2,000 mm. Results are rounded for display only; internal calculations retain full JavaScript precision. Entered measurements and assumptions determine the answer.

References and limitations

Renold, Transmission chain Installation, maintenance & designer guide (REN12, 2010). A primary chain-engineering reference for the pitch-line calculation. Its industrial guidance does not specify motorcycle chain selection, length or fitment.

This is a simplified pitch-line geometry estimate, not a ready-to-buy fitment or approval to modify/use a motorcycle. Many chains require an even pitch/link count, so 107 continuous-geometry planning pitches may not be a purchasable or compatible chain length. Verify chain type, link-count conventions, sprockets, tension, axle adjustment range and final length with the exact chain and motorcycle manufacturers or a qualified professional.

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This planner performs the stated arithmetic; it is not a vehicle inspection, engineering approval, manufacturer's recommendation or professional review.