# Chainring Diameter Calculator

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 formulaÂ

## 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:

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

- \(N\) 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.

**Answer:**

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.