Enter the number of teeth in the output gear and the number of teeth in the input gear into the Speed Ratio Calculator. The calculator will evaluate and display the Speed Ratio. 

Speed Ratio Formula

The following formula is used to calculate the Speed Ratio. 

SPR = OG / IG

  • Where SPR is the Speed Ratio
  • OG is the number of teeth in the output gear 
  • IG is the number of teeth in the input gear 

How to Calculate Speed Ratio?

The following example problems outline how to calculate Speed Ratio.

Example Problem #1:

  1. First, determine the number of teeth in the output gear. 
    • The number of teeth in the output gear is given as: 30.
  2. Next, determine the number of teeth in the input gear. 
    • The number of teeth in the input gear is provided as: 5.
  3. Finally, calculate the Speed Ratio using the equation above: 

SPR = OG / IG

The values given above are inserted into the equation below and the solution is calculated:

SPR = 30 / 5 = 6


Example Problem #2: 

For this problem, the variables required are provided below:

number of teeth in the output gear = 60

number of teeth in the input gear = 10

Test your knowledge using the equation and check your answer with the calculator above.

SPR = OG / IG = ?