Mountain bike chain length calculator

MTB Chain Calculator

For full-suspension bikes, use the length at full extension (no air/coil in the shock).
Use the same value for Min F and Max F for 1x systems (e.g., 32T).
Recommended Chain Links
—
Required Derailleur Capacity: —
Total Chain Length: —
Check your rear derailleur’s official capacity spec against the required capacity above.

How to Use the Mountain Bike Chain Length Calculator

This tool calculates the minimum number of chain links required and the total capacity your rear derailleur must handle for your specific gear setup.

Step 1: Measure Your Chainstay Length

The chainstay length is the distance between the center of your bottom bracket (crank axle) and the center of your rear axle.

  • Rigid (Hardtail) Bikes: Simply measure the center-to-center distance.
  • Full-Suspension Bikes (Crucial!): Since chainstay length changes with travel, you must use the measurement at Maximum Extension (the point where the rear axle is furthest from the bottom bracket). This usually means letting the air out of your rear shock and finding the longest distance.
  • Input: Enter the value in the Chainstay Length box and select either mm or inch.

Step 2: Input Your Maximum Gear Sizes (Length Calculation)

The maximum chain length is determined by the biggest gears that the chain must wrap around.

  • Largest Chainring (Max F): Enter the number of teeth on the largest chainring (front). For modern 1x systems, this is just the size of your single chainring (e.g., 32 or 34).
  • Largest Cog (Max R): Enter the number of teeth on the largest cog (sprocket) on your rear cassette (e.g., 50 or 52).

Step 3: Input Your Minimum Gear Sizes (Capacity Check)

These values are used to calculate the derailleur’s required chain wrap capacity.

  • Smallest Chainring (Min F): Enter the number of teeth on the smallest chainring. For 1x systems, this will be the same value as your Max F.
  • Smallest Cog (Min R): Enter the number of teeth on the smallest cog on your cassette (e.g., 10 or 11).

Step 4: Interpret the Results

Once all inputs are entered, the calculator will provide two key results:

  1. Recommended Chain Links:
    • This is the minimum number of links you should use. It is always rounded up to the nearest even number to ensure the chain is long enough and can be properly connected (since chains connect inner plate to outer plate).
  2. Required Derailleur Capacity:
    • This is the total difference in teeth that your rear derailleur must manage as you shift through all gears.
    • Action: You must check that the official specification for your rear derailleur (e.g., SRAM GX Eagle, Shimano XT) is equal to or greater than this required capacity. If your derailleur’s capacity is lower than this number, it will not function properly and could be damaged.
  3. Total Chain Length:
    • This shows the physical length of the chain (in mm or inches) corresponding to the recommended link count.