3D Printer XYZ Step Calibration Tool (Customizable) by geit_de - Thingiverse
On estep calibration - it varies by printing temperature, and do it under load (normal printing conditions, as opposed to with the bowden tube removed) : r/ender3
How to calibrate E steps on your extruder
Calibrating Your Makerbot using MatterControl | MatterHackers
How To Calibrate the Extruder Steps (Ender-3 / Ender-5 / CR-10) - Let's Print 3D