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Sprocket Ratio Calculator

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

About Sprocket Ratio Calculator

Chain drives are positive, so the tooth ratio sets the speed ratio exactly: output speed is input speed divided by N2/N1. Chain linear speed is teeth times pitch times rpm divided by 12, and it is the figure that governs lubrication method and permissible power.

Formulas

Speed and torque

Output rpm = input rpm x N1 / N2; torque multiplier = N2 / N1

Chain speed

V fpm = N1 x pitch in x rpm / 12

Worked example

With the default values below, Sprocket Ratio Calculator returns Output speed of 661.1. Change any input above and every figure here is recalculated in your browser.

Inputs used

Driving sprocket teethminimum 6
17
Driven sprocket teethminimum 6
45
Input speedminimum 1 rpm
1,750 rpm
Chain pitchminimum 0.1 in
0.5 in

Results

Output speed
661.1 rpm
Reduction ratio
2.6471
Chain speed
1,240 fpm
Torque multiplication
2.6471

Step by step

  1. 1Values used
  2. 2Speed and torque
  3. 3Chain speed
  4. 4Output speed= 661.1 rpm
  5. 5Reduction ratio= 2.6471
  6. 6Chain speed= 1,240 fpm
  7. 7Torque multiplication= 2.6471

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 4 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

How is the Sprocket Ratio figure worked out?

Output rpm = input rpm x N1 / N2; torque multiplier = N2 / N1. Chain drives are positive, so the tooth ratio sets the speed ratio exactly: output speed is input speed divided by N2/N1.

Why is 17 teeth a common minimum?

Fewer teeth means a larger articulation angle at each joint, which raises impact and wear sharply. Seventeen teeth is the usual practical floor for a power drive.

What values do I need to enter?

This calculator takes 4 inputs: Driving sprocket teeth, Driven sprocket teeth, Input speed, Chain pitch. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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