Now we have to do some mathWe need to find out how much filament your 3D printer actually extruded. This is calculated from: 120 mm - remaining filament distance (measured in the previous step). For me that was 120 - 27 = 93, for example. So my 3d printer only extruded 93 mm when I asked it to extrude 100 mm - that's 7% under extrusion! In order to calculate the new, correct extruder steps / mm, we carry out the following calculations. (Desired extruded filament / actually extruded filament = correction multiplier) in my case that would be 100/93 = 1.075 Next we calculate the E-steps (correction multiplier × original extruder steps / mm = calibrated extruder steps / mm) 1.075 × 1151 = 1237.325 steps (Depending on the extruder used, this value can be much smaller) These are our new extruder steps / mm! You can now save this value in your 3D printer, depending on the printer, the command: M92 E***.* (replace the * with your calculated extruder steps) followed by the command M500 to save the data permanently in the EEPROM. With some systems you have to enter this value in the configuration file of the 3D printer and save it. Finally, we test that the extruder is correctly calibrated, measure another 120 mm filament, mark this again and then extrude 100 mm. Now exactly 20 mm should remain. If not, try the above steps again.