Chain & Sprocket Ratio Calculator
What a chain run does to your speed and torque, and the one way it behaves differently from gears.
Inputs
A sprocket only fits the chain it was made for. Picking the type sets which sprockets you can choose.
Results
Chain ratio
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Driven : driving.
In lowest terms
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Output speed
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Relative to input speed.
Output torque
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Relative to input torque.
Rotation direction
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Compare this with a gear pair.
How this is calculated
The arithmetic is identical to a gear pair. Tooth counts are tooth counts, and chain does not change that.
ratio = driven teeth ÷ driving teeth speed = input speed ÷ ratio torque = input torque × ratioWith your numbers
The difference that catches people out
Two meshing gears turn in opposite directions. Two sprockets joined by a chain turn in the same direction.
This is the single most common cause of a drivebase that runs backwards on one side. If you replace a gear pair with a chain run and change nothing else, that side of the robot now drives the other way. If you only did it to one side, the robot spins instead of driving straight. The fix is in software or in your motor reversal, not in the chain.
When chain is the right answer
Chain moves power across distances that would need a long, heavy, and poorly-supported gear train. It tolerates imprecise shaft spacing far better than gears, which must sit at an exact center distance. The trade-offs are that chain stretches, can skip teeth under shock load, and throws itself off the sprockets if it runs slack.
On a drivebase specifically, chain is most often used to link multiple wheels on the same side, rather than as the primary reduction from the motor.
Sources & assumptions
Tooth counts and outer diameters are the confirmed contents of the VEX High Strength Sprocket & Chain Kit (276-2252). Outer diameters are approximate as listed by the supplier, and are shown to help you identify a sprocket in hand. They are not used in any calculation on this page.
Assumes a simple two-sprocket run with no idlers or tensioners. Adding an idler changes neither the ratio nor the direction, since an idler on a chain run only takes up slack.
- VEX High Strength Sprocket & Chain Kit (276-2252) — kit contents — checked 2026-08-17
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Collects what you entered, what came out, how it was worked out, and anything the tool flagged, with a timestamp and a version so someone else can reproduce it.
This is evidence, not a notebook entry. It deliberately does not write your problem statement, your reasoning, or your conclusion, because under RECF rules an Engineering Notebook has to be the students' own work and no tool may generate or organise its content. Take the numbers, decide what matters, and write it yourself.