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Motorcycle Chain Sprocket Ratio Calculator

Work out motorcycle chain sprocket ratio instantly with clear inputs, formula shown and shareable results.

About Motorcycle Chain Sprocket Ratio Calculator

Final drive ratio is rear teeth over front. Changing the front sprocket by one tooth alters the ratio by 6% or more, while one tooth on the rear changes it by about 2% — which is why front sprocket changes are the blunt instrument and rear changes the fine adjustment.

Formula

Final drive

ratio = rear teeth / front teeth; one front tooth is worth about three rear teeth

Worked example

With the default values below, Motorcycle Chain Sprocket Ratio Calculator returns Final drive ratio of 2.81. Change any input above and every figure here is recalculated in your browser.

Inputs used

Front sprocket teeth
16 teeth
Rear sprocket teeth
45 teeth
Engine speed
6,000 rpm
Rear tyre circumference
1,980 mm

Results

Final drive ratio
2.81 :1
Speed at that engine speed
298.17 km/h
Change if the rear gains one tooth
2.22% %
Extra chain length needed
37.70 mm

Step by step

  1. 1Values used
  2. 2Final drive
  3. 3Final drive ratio= 2.81 :1
  4. 4Speed at that engine speed= 298.17 km/h
  5. 5Change if the rear gains one tooth= 2.22 %
  6. 6Extra chain length needed= 37.70 mm

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

Should I change the front or the rear?

Rear for fine tuning, front for a big change. A smaller front sprocket also increases chain wear because of the tighter wrap angle.

What does gearing down achieve?

Quicker acceleration and lower top speed, with higher cruising rpm and worse economy. Gearing up does the reverse.

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