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Calcimator

Motorcycle Gear Ratio

Calculate speed per RPM for different sprocket combinations.

Inputs

mm
RPM

Results

Speed

127.8 km/h

Speed

79.4 mph

Final Drive Ratio3
Overall Ratio5.52
RPM per km/h47
Rear +1 Tooth Change2.2%
Rear -1 Tooth Change-2.2%
How to Use This Calculator
  1. Enter Front Sprocket Teeth, Rear Sprocket Teeth, and Primary Drive Ratio.
  2. Set Gearbox Ratio (Current Gear), Tire Circumference, and Engine RPM.
  3. Review Speed (km/h) and Speed (mph).
  4. Use Final Drive Ratio and Overall Ratio to inform your decision.

How the result changes with Rear Sprocket Teeth

Rear Sprocket TeethSpeedSpeed
34169.2 km/h105.1 mph
44130.7 km/h81.2 mph
56102.7 km/h63.8 mph
6687.2 km/h54.2 mph

What each input means

Front Sprocket Teeth
Countershaft (front) sprocket tooth count.
Rear Sprocket Teeth
Rear sprocket tooth count.
Primary Drive Ratio
Primary drive ratio from engine to gearbox (check service manual).
Gearbox Ratio (Current Gear)
Transmission ratio for the gear you want to calculate (1.0 for top gear if 1:1).
Tire Circumference
Rear tire rolling circumference in mm.
Engine RPM
Engine speed to calculate road speed at.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Front Sprocket Teeth = 15, Rear Sprocket Teeth = 45, Primary Drive Ratio = 1.84, Gearbox Ratio (Current Gear) = 1 = 6 input(s) provided
  2. Calculate Speed
    Speed
    127.8 = 127.8
  3. Calculate Speed
    Speed
    79.4 = 79.4
  4. Calculate Final Drive Ratio
    Final Drive Ratio
    3 = 3
  5. Calculate Overall Ratio
    Overall Ratio
    5.52 = 5.52

Engine last updated . Checked against 1 independently-derived test — how we verify calculators.

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