Velopedia Tools

Chain Length

Bicycle Chain Length Calculator

Estimate the large-chainring/large-sprocket chain path from bicycle geometry, account for suspension chain growth, and turn the add-link instruction from your derailleur manual into a practical chain-cutting worksheet.

Drivetrain

Use the largest chainring and largest rear sprocket the chain must accommodate.

Largest chainring teeth Largest rear sprocket teeth

Frame geometry

The effective bottom-bracket-to-rear-axle distance is what matters to chain growth.

Frame type BB to rear axle mmMeasure center-to-center at the normal/static frame position

Service procedure

The calculator does not guess the add-link rule for your derailleur.

Drivetrain reference Drivetrain layout Manual add-links linksLeave blank for geometry only. Enter the number only after checking the instructions for your exact derailleur. New chain length linksLink count printed on the replacement-chain package

Chain sizing worksheet

Your Results

Enter the drivetrain and frame dimensions to calculate the geometric chain-path baseline.

Before cutting a chain

Confirm the exact rear-derailleur sizing procedure.
On full suspension, check the point of maximum BB-to-axle distance.
Do not confuse a brand's inner/outer-link wording with an arbitrary link allowance.
Confirm the connecting-link orientation and reuse rules.
Cycle the suspension and verify large/large capacity before riding.

What this calculator actually computes

The geometry model estimates the chain length needed to span the chainring, rear sprocket and bottom-bracket-to-axle distance. It deliberately keeps that calculation separate from the extra links required by a specific derailleur. That distinction matters: the geometry of the bicycle can be calculated, but the amount of cage movement and setup allowance is a component-system decision.

L = 2C + (F + R) / 4 + (F − R)² / (4π²C)L and C are in inches; F and R are tooth counts. The result is converted to 1/2-inch chain pitches and rounded upward to a usable even link count.

Why full suspension changes chain sizing

Rear-suspension motion can move the rear axle farther from the bottom bracket than the static geometry number suggests. A chain that is safe at sag can become too short elsewhere in the travel. For that reason, Velopedia will show the static estimate but will not label a full-suspension result cut-ready until a maximum BB-to-axle distance is supplied.

Manufacturer procedures are not interchangeable

SRAM Eagle AXS

SRAM's non-T-Type Eagle AXS procedure uses a physical large-chainring/large-cog wrap and changes the added inner/outer links between hardtail and full-suspension bikes.

SRAM Road AXS

SRAM's Road AXS instructions also use the physical large/large wrap, with different additions for 1× and 2× systems.

SRAM Transmission

Full Mount/T-Type is a special case. SRAM directs mechanics to the Full Mount Chain Length Guide or AXS app and may return frame-specific chain length and setup information.

Shimano

Shimano publishes chain-sizing instructions in the dealer manual for the applicable derailleur. The required addition varies by system, so verify the exact model rather than applying one generic Shimano number.

How to use the planning candidate

First calculate the geometric baseline. Then check the service instructions for the exact drivetrain. If that procedure gives an explicit number of additional links that you want to compare with the geometry model, enter it in Manual add-links. The planning candidate rounds upward to an even number of conventional half-inch chain links and shows how many links would be removed from the entered stock-chain length. It remains a cross-check; the manufacturer's physical sizing procedure is the final reference.

Current service references: Shimano Service Information · SRAM Eagle AXS chain sizing · SRAM Road AXS manual · SRAM Eagle Transmission manual