Use this derailleur capacity calculator to check chain wrap and largest-cog compatibility before changing cassette, chainrings, or rear derailleur.
Derailleur Capacity Calculator
Check chain wrap capacity for 1x and 2x drivetrains before changing cassette, chainrings, or rear derailleur.
How to use this calculator
Enter the values that match your bike, body, route, training data, or shipping box. Change one input at a time if you want to see which detail moves the result most.
What the result means
A passing result means the basic capacity math works. It does not guarantee shifting, because hanger geometry, B-screw range, drivetrain family, chain length, and cassette spacing still matter.
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This calculator is for practical planning and comparison. It does not replace a professional bike fit, mechanic inspection, medical guidance, carrier quote, manufacturer specification, or local safety judgment.
