Sprocket ratio is the __________ the driven sprocket divided by that of the drive sprocket.

• A. Number of teeth on
• B. Ratio of sprocket diameters
• C. Circumference ratio
• D. The number of teeth on the driven sprocket divided by the number of teeth on the drive sprocket

Answer: (D)

In a chain drive, the sprocket ratio describes how many times the driven sprocket turns for each turn of the drive, which comes from dividing the number of teeth on the driven sprocket by the number of teeth on the drive sprocket. Since the chain engages one tooth per pitch, the rotation speed is set by how many teeth each sprocket has: more teeth on the driven sprocket means it turns more slowly for the same chain movement, and fewer teeth means it turns faster. This ratio directly links tooth counts to the speed and torque relationship between the two sprockets.

For example, if the driven sprocket has more teeth than the drive sprocket, the ratio is greater than one, giving a speed reduction but torque increase on the driven side. If the driven has fewer teeth, the ratio is less than one, giving a speed increase.

The ratio is fundamentally about tooth counts, and while diameter or circumference can reflect the same relationship when the chain pitch is constant, the standard definition uses the number of teeth on each sprocket.