Chain Length Calculator

Measure your chainstay length from bottom bracket center to rear axle center. Count the teeth on your largest front chainring and largest rear cog. Apply the formula: 2 × chainstay length + (front teeth ÷ 4) + (rear teeth ÷ 4) + 1. This gives length in inches. Divide by 0.5 and round up to get the number of links. For a bike with 16" chainstays, 50 front teeth, and 30 rear teeth, that's 2 × 16 + 12.5 + 7.5 + 1 = 53 inches or 106 links.

A chain that's too long creates excessive slack in your small-small gear combination. This causes poor shifting performance, chain slap against the frame, and the risk of the chain dropping off the chainring or cassette. The derailleur can't take up enough slack, leaving the chain loose and prone to falling off during rough terrain or aggressive pedaling. Even one or two extra links can cause issues, especially on bikes with short-cage derailleurs.

Only if both bikes use the same number of speeds. An 11-speed mountain bike chain works on an 11-speed road bike because they share the same external width and pitch. However, mountain bike chains often cost less and may not shift as smoothly on road bike drivetrains due to different chamfering and coating. Match the chain speed (9-speed, 10-speed, 11-speed, etc.) to your cassette first, then consider whether MTB or road-specific chains work better for your riding style.

Most adult bikes need 106-116 links depending on frame size, chainstay length, and gearing. Small frames with short chainstays and compact gearing might need 100-104 links. Large frames with long chainstays and wide-range cassettes can require 116-120 links. Single-speed bikes typically use fewer links (90-100) since they don't need to accommodate a derailleur. Calculate your specific need rather than guessing—the formula accounts for your bike's unique geometry.

The standard formula is: chain length = 2 × (chainstay length) + (largest front teeth ÷ 4) + (largest rear teeth ÷ 4) + 1. This gives length in inches. For bikes with chainstays shorter than 15 inches or extreme gear ratios, use the rigorous formula: chain length = 2 × √(chainstay² + (0.0796 × (front teeth - rear teeth))²) + (front + rear teeth) ÷ 4. Both formulas assume measurements in inches and require converting the result to links by dividing by 0.5 and rounding up.

Use a tape measure or ruler to measure from the center point of the bottom bracket (where the crank arms attach) to the center point of the rear axle (where the wheel mounts). This measurement is typically between 15-18 inches for most bikes. On full-suspension mountain bikes, measure with the suspension at sag (your weight on the bike) rather than fully extended. Convert any fractional measurements to decimals before using them in the formula: 16 1/4" becomes 16.25", 17 3/8" becomes 17.375".

Yes, most bike chain length calculators available online are completely free to use with no registration required. These calculators handle the math automatically when you input your chainstay length, front chainring teeth, and rear cog teeth. They typically provide results in both inches and number of links, often showing both the simple and rigorous formula results. Many also include features like fractional-to-decimal converters and gear combination charts.

Always round up when converting chain length to links. If your calculation shows 107.3 links, use 108 links. A chain that's one link too long is far better than one that's too short. You can remove an extra link easily if the chain has too much slack, but you can't add a link if the chain is too short without buying a new chain. The only exception is single-speed bikes where you need exact tension—in that case, use the wheel's position in the dropouts to fine-tune the length.

Measure chain wear using the 12-inch ruler test: place the 0-inch mark at a pin center, then check where the 12-inch mark falls. If the pin center sits past the 12 1/16-inch mark, replace the chain. If it's beyond 12 1/8 inches, you've also damaged the cassette and chainrings. Proper length adjustment only matters if the chain still has good wear measurements but shifts poorly due to incorrect sizing. New chains stretch slightly in the first 50-100 miles, which is normal break-in and doesn't require adjustment.

The length calculation is the same regardless of chain speed—both use the same formula based on chainstay length and gear teeth. The difference between 10-speed and 11-speed chains is the external width, not the length. An 11-speed chain is narrower (approximately 5.5mm external width vs. 6.2mm for 10-speed) to fit between the more closely-spaced cogs on an 11-speed cassette. Always use a chain that matches your cassette speed, but calculate the length the same way for both.

Yes, you can shorten a chain by removing links using a chain breaker tool. Remove an even number of links (usually 2 or 4) to maintain proper inner-outer link pairing. If your chain uses a master link, remove it first, then use the chain tool to push out pins and remove the desired links. Reinstall the master link to reconnect the chain. Test shifting through all gears after shortening to ensure proper derailleur capacity and no rubbing in extreme gear combinations.

Full-suspension mountain bikes need extra chain length because the rear triangle moves as the suspension compresses, effectively lengthening the chainstay. Measure the chainstay with the suspension at sag (your weight on the bike) and add 1-2 links to the calculated length. The derailleur's clutch mechanism manages the extra slack in the extended position. Without these extra links, the chain pulls tight when the suspension compresses fully, potentially damaging the derailleur or causing the chain to break under load.