Extruder steps per mm calculator for E-step calibration

What this calculator does

Extruder calibration is one measurement and one ratio. Mark the filament, command 100 mm, measure what actually went in. If 96.5 mm went in from a setting of 93 steps per millimetre, the corrected value is 96.373 and the printer was under-extruding by 3.5 per cent on every print it has ever made.

The common mistake is fixing this in the slicer instead. Dropping the flow rate to 103 per cent hides the symptom and leaves the firmware wrong, so the error reappears the next time you slice something in a different profile. Calibrate the steps once in the firmware and leave the flow multiplier at 100 per cent, where it belongs for material differences rather than machine ones.

The formula

Formulacorrected steps = current steps × commanded length ÷ length actually extruded

The extruder moves a distance proportional to the steps it is told to take, so if the real extrusion is short, the steps per millimetre were too low in exactly that proportion. The correction is current steps × commanded length ÷ length actually extruded. Because it is a ratio rather than a difference, the percentage error is the same whatever extruder you are on, while the size of the correction scales with the steps value.

Term	Meaning
Steps per mm	Firmware figure for how many motor steps push one millimetre of filament. Often called E-steps.
Commanded length	What you asked for, usually 100 mm so the arithmetic is obvious.
Under-extruding	Less filament went in than was asked for, so the steps value is too low.
Flow rate	Slicer multiplier for material differences. Not the place to fix a calibration error.

The inputs explained

Field	What to enter
Current steps per mm	The steps per mm currently in the firmware. Read it back rather than trusting the profile.
Length commanded (mm)	The length you commanded. One hundred millimetres keeps the percentages easy to read.
Length actually extruded (mm)	Measured filament consumed, from the mark to the entry point. Measure with calipers if you can.

When to use it

Calibrating a new printer

Mark the filament 120 mm above the extruder entry, extrude 100 mm slowly with the nozzle hot, then measure what is left. Enter the three numbers and write the result to firmware.

Chasing under-extrusion

Run the test before changing anything else. A 3 to 5 per cent E-step error looks exactly like a partial clog and is far more common.

After changing extruder or gearing

A new extruder changes the gearing, so the old value is meaningless. Recalibrate rather than scaling the old number.

Worked examples

Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.

What steps value does a measured test give?

Only the measured extrusion changes.

Starting from 93 steps per mm, 100 mm commanded

Measured extrusion	Corrected steps per mm	Error before correction	Direction
90 mm	103.333	10.0%	under-extruding
95 mm	97.895	5.00%	under-extruding
98 mm	94.898	2.00%	under-extruding
100 mm	93.000	0.000%	already calibrated
102 mm	91.176	2.00%	over-extruding
105 mm	88.571	5.00%	over-extruding

An extrusion 10 mm short of 100 raises 93 steps to 103.333, and one that overshoots to 105 lowers it to 88.571. The two 5 per cent rows look symmetric and are not: 95 mm measured gives 97.895, which is 4.895 up, while 105 mm gives 88.571, which is 4.429 down. That is because the error divides rather than subtracts. A measurement of exactly 100 leaves the value untouched.

Does the correction depend on the extruder?

The same test result applied to four different starting values.

100 mm commanded, 96.5 mm measured, across four extruder types

Current steps per mm	Corrected steps per mm	Change from the current value	Error before correction
93 steps/mm	96.373	+3.373	3.50%
140 steps/mm	145.078	+5.078	3.50%
415 steps/mm	430.052	+15.052	3.50%
830 steps/mm	860.104	+30.104	3.50%

The percentage error belongs to the test rather than to the machine, so all four rows read 3.50 per cent. What changes is the size of the correction: a 93-step Bowden setup moves by 3.373 steps and an 830-step geared direct drive by 30.104. If you are comparing notes with someone on different hardware, compare the percentages, because the step counts are not comparable at all.

Questions

How far above the extruder should I mark the filament?

Further than you intend to extrude, so 120 mm for a 100 mm test. Then measure from the mark to the entry point afterwards and subtract, rather than trying to measure the filament that has gone.

Why extrude slowly?

Because a fast extrusion under-extrudes for reasons calibration cannot fix, such as the melt rate and back pressure. Around 100 mm a minute is slow enough that the only thing you are measuring is the gearing.

Should the nozzle be hot?

Yes, at printing temperature, and the test should push plastic out of the nozzle rather than into free air through a removed hotend. The idler tension should be whatever you normally print with.

What error is worth correcting?

Anything above about half a per cent. At 3.5 per cent, a 50 g print is off by 1.8 g of plastic, which shows up as thin walls and poor layer bonding well before it shows up on the scales.

Do I still need to tune the flow rate afterwards?

Possibly, but for a different reason. Once the steps are right, the flow multiplier is there to account for a particular filament, and it should sit close to 100 per cent rather than carrying a machine error.

For what the corrected value means in material, see filament weight and cost. Maximum volumetric speed covers the other common cause of under-extrusion, and shrinkage compensation deals with dimensional error that is not the extruder.