CalculatorsDerailleur Capacity Calculator
Derailleur Capacity Calculator
Capacity is how much slack the cage must swallow between big-big and small-small. A 1× setup uses the same tooth count for both chainring fields.
Inputs
Results
- Total capacity
- 39 T
- Cage code
- 3
How the number is made
Capacity = (big ring − small ring) + (big cog − small cog). Cage code 1 is a short cage up to 33 T, 2 is medium up to 37 T, 3 is long up to 47 T, 4 exceeds those bands.
Published cage capacities differ by brand. Treat 33/37/47 as Shimano-like bands, then read the derailleur sheet.
- Cage code. 1 short (≤33), 2 medium (≤37), 3 long (≤47), 4 over 47.
Related calculators
- Optimal Chain Length Calculator
Capacity without the right link count still skips.
- Cassette Range Calculator
A 520% cassette is a capacity problem before it is a marketing number.
Questions
What if I only have one chainring?
Enter it as both the large and the small ring. Capacity is then just the cassette spread.
Is a longer cage always safer?
It wraps more chain. It can also hang closer to rocks. Use the shortest cage that clears your capacity.
What cage does 52/36 with 11-34 need?
Capacity is (52 minus 36) plus (34 minus 11), which is 39 teeth. That is cage code 3, because 37 is the top of the medium band.
Related gear
- Rear derailleur
Match speeds and max cog as well as total capacity.
$40–$250