Chainring Diameter Calculator

Chainring Diameter Calculator

Chainring Diameter Calculator

Created by Team y2calculate

Content  written by Mason (Bike Catalogue)

Calculator code by Marcelino 

Reviewed by Sajid khan

Fact checked 🔍✓

Published: January 31, 2024 → Last Updated: February 5, 2024

we have made the following chainring diameter table keeping the pitch length 0.5 inches or 12.7 mm. Most of the time the pitch length is not more than or less than 0.5 inches so we took it as a constant number for the given table.

If you think that your pitch length is smaller or longer than 0.5 inches, use the above calculator by entering the total teeth number and chain pitch (which is the distance between the centers of two consecutive links in a roller chain)

You can also calculate chainring diameter manually by using this formula 

No of teeth Diameter (mm) Diameter (inches)
16 teeth
69.68 mm
2.74 inches
18 teeth
77.77 mm
3.06 inches
20 teeth
85.85 mm
3.38 inches
22 teeth
93.94 mm
3.70 inches
24 teeth
102.02 mm
4.02 inches
26 teeth
110.11 mm
4.33 inches
28 teeth
118.19 mm
4.65 inches
30 teeth
126.28 mm
4.97 inches
32 teeth
134.36 mm
5.29 inches
34 teeth
142.45 mm
5.61 inches
36 teeth
150.53 mm
5.93 inches
38 teeth
158.62 mm
6.24 inches
40 teeth
166.70 mm
6.56 inches
42 teeth
174.79 mm
6.88 inches
44 teeth
182.87 mm
7.20 inches
46 teeth
190.96 mm
7.52 inches

Formula for chainring diameter with example

The formula to calculate the chainring diameter (\(CD\)) given the number of teeth (\(N\)), chain pitch (\(CP\)), and chain link height (\(CLH\)) is:

\[ CD = \left(\frac{N \times CP}{\pi}\right) + CLH \]


  • \(N\) is the number of teeth on the chainring.
  • \(CP\) is the chain pitch, which is the distance between the centers of two consecutive links in a roller chain, measured in millimeters or inches.
  • \(CLH\) is the chain link height.

Find the chainring diameter (\(CD\)) for \(N = 40\) teeth, \(CP = 8\) millimeters, and \(CLH = 5\) millimeters.


Using the chainring diameter formula:

\[ CD = \left(\frac{40 \times 8}{\pi}\right) + 5 \approx 136.78 \text{ millimeters} \]

Therefore, the chainring diameter is approximately \(136.78\) millimeters.

Note: The addition of \(5\) millimeters accounts for the chain link height, providing the outer circumference of the chainring.If you thinks that your chain link height is smaller or bigger than 5mm, than replace the 5mm with your chain link height.

What is chainring diameter

The chainring diameter refers to the size or diameter of a circular disc with teeth on a bicycle crankset. It is an important component that, along with the rear cassette, determines the gear ratio and affects the bike’s pedaling efficiency and overall speed.

Want to know more about chainring watch this video

Embedded YouTube Video
Why is chainring diameter important?

Chainring diameter is crucial because it, along with the rear cassette, influences the gear ratio. The gear ratio affects how much effort is required for pedaling, impacting the bike’s performance in different riding conditions.

What role does chainring diameter play in gearing?

Chainring diameter, when combined with the rear cassette, determines the gear ratio. A larger chainring provides a higher gear, suitable for flat terrain and high speeds, while a smaller chainring offers a lower gear, ideal for climbing or challenging terrains.

Can I change the chainring diameter on my bike?

Yes, many bikes allow for chainring upgrades or replacements. However, it’s essential to consider compatibility with your bike’s drivetrain, as changing the chainring diameter can affect the overall gear ratio.

Are chainring diameters standardized across all bikes?

No, chainring diameters can vary between different bicycle models and types. Common sizes include 53/39T for road bikes and 32T for mountain bikes. It’s essential to check your bike’s specifications for the appropriate chainring diameter.

Can I mix different chainring diameters on my bike?

Mixing chainring diameters may not be recommended unless your bike’s drivetrain is designed for it. Incompatibility can lead to shifting issues and affect the overall performance of the bike.

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