How To Measure Chainstay Length For Chain Calculation

To measure chainstay length, measure straight from the center of the bottom bracket to the center of the rear axle in a straight line, which typically ranges from 400mm to 460mm on most adult bikes.

Chainstay length is one of the key inputs for calculating bike chain length. Getting an accurate measurement ensures your chain will be sized correctly for smooth shifting and proper tension.

What is Chainstay Length?

The chainstay is the tube that runs from your bottom bracket (where the pedals attach) to your rear wheel axle. Chainstay length is the distance between these two points measured in a straight line.

Typical chainstay lengths:

Road bikes: 400-415mm
Gravel bikes: 420-435mm
Mountain bikes (hardtail): 425-445mm
Mountain bikes (full suspension): 430-475mm
BMX: 350-380mm

Tools You'll Need

Tape measure (preferably metal) or
Calipers (for precision) or
String and ruler (backup method)

A metal tape measure is ideal because it stays straight during measurement.

Step-by-Step Measurement

Step 1: Prepare Your Bike

Place your bike on a level surface
Make sure the rear wheel is properly seated in the dropouts
For full suspension bikes, set the suspension to sag position or note if you're measuring at full extension

Step 2: Locate the Bottom Bracket Center

The bottom bracket center is at the center of the spindle where your cranks attach.

How to find it:

Look at where your pedal crank arms attach to the frame
The center point is at the axis of rotation
On most bikes, this is at the center of the round bottom bracket shell

Step 3: Locate the Rear Axle Center

The rear axle center is at the middle of your rear wheel's axle.

How to find it:

Look at your rear hub
The center is at the axle itself, not the dropout edges
For quick-release, it's at the skewer center
For thru-axle, it's at the axle center

Step 4: Measure the Distance

Hold the tape measure from the center of the bottom bracket to the center of the rear axle. Keep the tape straight; do not follow the curve of the chainstay tube.

Tips for accuracy:

Measure from the drive side (right side) of the bike
Keep the tape taut but don't pull excessively
Take 2-3 measurements and average them

Step 5: Record Your Measurement

Note your chainstay length in millimeters. If your tape measure shows inches, you can convert:

Multiply inches by 25.4 to get millimeters
Or use our calculator which accepts both units

Alternative Methods

Method 1: Use Manufacturer Specifications

Many bike manufacturers publish geometry charts that include chainstay length:

Find your bike's model and size
Check the manufacturer's website
Look for "geometry" or "specs"
Find "chainstay length" or "CS" in the table

Advantages: Very accurate, no measuring needed Disadvantages: May not account for frame variations or modifications

Method 2: String Method

If you can't get a tape measure to the right spots:

Hold a piece of string from BB center to axle center
Mark where the string reaches the axle
Lay the string flat and measure the marked length

Method 3: Calipers for Precision

For the most accurate measurement:

Use a long caliper or measuring rod
Place one end at the BB center
Extend to the axle center
Read the measurement directly

Common Measurement Mistakes

1. Measuring the Chainstay Tube

Wrong: Measuring along the curved chainstay tube Right: Measuring in a straight line between centers

The chainstay tube is longer than the chainstay length because it curves.

2. Measuring from the Wrong Points

Wrong: Edge of bottom bracket shell, edge of dropout Right: Center of BB spindle, center of rear axle

3. Not Accounting for Wheel Position

Wrong: Measuring with wheel not fully seated Right: Ensuring wheel is properly in dropouts

For horizontal dropouts, measure with the wheel in your intended position.

4. Ignoring Suspension State (Full Suspension)

Wrong: Measuring at random suspension position Right: Measuring at sag or noting which position you used

See our Full Suspension Chain Length Guide for details.

Full Suspension Bikes: Special Considerations

For full suspension mountain bikes, chainstay length changes as the suspension moves:

Suspension Position	When to Use
Full extension	Maximum chain length needed
Sag (25-30%)	Normal riding measurement
Full compression	Check chain doesn't bind

Recommendation: Measure at sag, then add 2-4 links for compression clearance.

Converting Between Units

Our Bicycle Chain Length Calculator accepts both metric and imperial units, but here are conversions if needed:

Millimeters	Inches
400mm	15.7"
410mm	16.1"
420mm	16.5"
430mm	16.9"
440mm	17.3"
450mm	17.7"
460mm	18.1"

Typical Chainstay Lengths by Bike Type

Road Bikes

Category	Typical Range
Race/aero	400-405mm
Endurance	405-420mm
Touring	420-450mm

Mountain Bikes

Category	Typical Range
XC hardtail	420-435mm
Trail hardtail	430-445mm
Trail full suspension	435-450mm
Enduro	440-475mm
Downhill	430-445mm

Gravel and Cyclocross

Category	Typical Range
Race CX	410-420mm
Gravel	420-435mm
Adventure	430-450mm

Using Your Measurement

Once you have your chainstay length, you can:

Use the calculator: Enter it into our Bicycle Chain Length Calculator
Apply the formula: L = 2 × C + (F + R) / 4 + 1 (see our formula guide)
Check the charts: Cross-reference with our Chain Length Chart

Quick Summary

Find the center of your bottom bracket
Find the center of your rear axle
Measure straight between them (not along the tube)
Record in millimeters
Use this value in the chain length formula or calculator

How To Calculate Bike Chain Length - Use your measurement
Bicycle Chain Length Calculator - Instant calculation
Bike Chain Length Chart - Quick reference
Full Suspension MTB Chain Length - Special considerations
Is Your Chain Too Long or Too Short? - Troubleshooting