Calculate gear ratio

Hello friends.
Currently, I am having a hard time calculating the gear ratio in Code Marlin for the Z axis. I ask you to calculate and help me with the formula so that I can calculate it.
I have an A4988 Driver with a microstep of 1/16
The motor I use is Nema 17 1.8 degrees
Puley I attached to Nema 17 is 20 teeth connected to 1 Puley has 60 teeth
Used standard belt is GT2 step 2mm
So I will have to calculate how to be able to move the number of pulses corresponding to 1mm. Do you have a formula or standard way to help me?

I can’t anaswer your question since I’m not knowledge abot motors / mechanical engineering, but maybe sites like or can get you better answer.