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What extruder steps are and why they drift
Your printer’s extruder moves filament by turning a motor a precise number of steps. The setting that links motor steps to millimetres of filament is called extruder steps per millimetre, usually written as E-steps. If this number is wrong, every print is wrong in the same direction: the printer thinks it pushed 100 mm of filament when it really pushed 96 mm, or 104 mm. The result is under-extrusion or over-extrusion on every single print, no matter how good the model or the slicer settings are.
E-steps drift for ordinary reasons. A new extruder gear, a different gear diameter, a firmware update that resets values, or a printer assembled from a kit can all leave the number off. The error is invisible in decorative prints, where a little too much or too little plastic barely shows, but it ruins functional parts. Holes shrink, walls thicken, and mating parts refuse to fit. That is why E-steps calibration is the first calibration to do on any printer, before flow rate, before temperature towers, before anything else.
How to run the 100 mm test
Heat the nozzle to the printing temperature for your filament, because cold filament will not move and the test will fail. Mark the filament 120 mm above the extruder entry point with a pen, so the mark is visible and measurable. Then command the printer to extrude 100 mm, slowly, through its controls or a terminal command. When it stops, measure from the extruder entry to your mark. If the mark is now 20 mm above the entry, exactly 100 mm went in and your E-steps are correct. If it is 24 mm above, only 96 mm went in, and you are under-extruding.
Measure carefully and repeat the test once. Filament can slip on the first run, especially if the extruder gear is dirty or the filament path is tight. If the two runs disagree by more than a millimetre, clean the gear teeth and check that the filament moves freely, then test again. The calculator takes your current E-steps, the length you requested, and the length actually extruded, and gives the corrected value. In the example above, with current steps of 93, the corrected value is 93 times 100 divided by 96, which is 96.88 steps per mm.
A worked example
Take a printer with 93 steps per mm that extrudes only 96 mm when asked for 100 mm. The error is minus 4 percent, and the corrected steps are 96.88. Enter that value, save it to the printer’s memory, and run the test again. The second run should deliver 99 to 101 mm, which is good enough. If it delivers 98 mm, one more correction, 96.88 times 100 divided by 98, gives 98.86, and the third run should land on target. Two rounds is normal, and chasing the last fraction of a millimetre is not worth it.
Now consider the opposite case: the printer extrudes 106 mm when asked for 100 mm. The corrected steps are 93 times 100 divided by 106, about 87.74. Over-extrusion at the extruder level explains a whole set of symptoms: blobs, stringing that will not go away, and dimensions that are consistently too large. Fixing the number at the source clears symptoms that no slicer tweak can properly fix, because every slicer setting was compensating for the same underlying error.
Where to save the new value
Save the corrected E-steps in the printer’s firmware settings if your printer allows it, so the value survives power cycles and applies to every print. If your printer resets settings on reboot, put the value in your slicer’s start code instead, where it is applied at the start of every print. Do not set it in both places with different values, or they will fight. Write the value down somewhere safe, with the date and the filament used, because a future firmware update may reset it without warning.
Be careful with one trap: calibrating E-steps with the nozzle removed or with no filament resistance gives a different number than real printing. Always calibrate with the nozzle at temperature and filament loaded, as close to real conditions as possible. Also note that flexible filaments like TPU compress and slip more than rigid ones, so a value calibrated with PLA may not transfer exactly to TPU. Calibrate per material family when accuracy matters.
Frequently asked questions
How often should I calibrate E-steps? Once when the printer is new, again after any extruder change, and once a year as a check. It does not drift on its own if nothing changes.
Do I still need flow calibration after E-steps? Yes. E-steps fixes how much filament the extruder delivers. Flow calibration then fixes how that filament behaves as it leaves the nozzle, which varies by material.
Why does my printer extrude less when printing fast? At high speeds the hot end cannot melt filament fast enough, so the extruder skips. That is a speed and temperature limit, not an E-steps error, and it needs slower printing or a hotter nozzle.
These figures are estimates and general guidance only, not a guaranteed print result. Your filament manufacturer’s datasheet and your printer’s own calibration govern every setting. Use the calculator above with your measured extrusion, save the corrected steps, and verify with a second 100 mm test.
Related calculators
- Spanish version
- Extrusion Calibration Calculator – Corrected Flow from Measured Wall Thickness
- Infill Weight Calculator – Filament Weight from Infill Percentage Alone
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