How do I calculate E steps?

Filament 3D Printer Technical Help Creality Ender 3 / 3 Pro / V2
1

Just upgraded my firmware after installing the BL touch on my Ender 3 V2, now it seems to be under-extruding.

2

Web based calculator.
https://www.th3dstudio.com/estep-calculator/

3

very similar but also available from teaching Tech

https://teachingtechyt.github.io/calibration.html#esteps