Hey there @Ad2Box -- great question. Welcome to Calendly Community! 

We are unable to track conversions using Google Tag Manager, but you can track conversions by using our UTM Parameters. With a Calendly account, you can track conversions directly within Calendly by adding UTM (Urchin tracking module) parameters to your scheduling links.Use these steps to build your link to track conversions:

1. First, define which UTM codes you want to append to your link.
2. Once you’ve defined what UTM codes you’d like to use, you can append them to the end of your Calendly link by adding a '?' after the link.
3. Then, add your UTM codes using ‘&' to separate each new code. (i.e. utm_medium=social&utm_source=facebook)Use ‘%20’ to add spaces to your codes (i.e. utm_campaign=”summer%20promotion is a UTM code for a summer promotion campaign). Your link could look something like this: www.calendly.com/yourlink?utm_medium=social&utm_source=facebook&utm_campaign=”summer%20promotion
4. To track conversion of these links, from your Home page select Scheduled Events.
5. Select Filter. Then, under Tracking IDs, select All IDs and enter the UTM code(s) you’d like to track.

Once you’ve filtered your scheduled events, you can export the data to a CSV file you can use in a spreadsheet.

 Note: There is a 255 character limit for UTM values. Any values that exceed this limit may not be passed.

I hope this helps!