Pressure Advance Calibration Calculator

Frequently Asked Questions

What is pressure advance (PA) / linear advance (LA)?

PA (Klipper) and LA (Marlin) pre-compensate for pressure buildup in the melt zone so extrusion speed matches head speed during acceleration. Tuned correctly, corners and seams sharpen and bulging stops.

How do I tune PA from a tower test?

Print a PA tower that ramps PA from 0.0 to 0.1 (direct drive) or 0.0 to 1.0 (Bowden) over height. Pick the height where corners look sharpest without under-extrusion gaps, then convert height → PA value using the test's step rate.

Typical PA values by setup?

Direct drive: 0.02–0.06 for most filaments. Bowden: 0.30–0.80. PETG tends to need slightly higher PA than PLA on the same machine; ABS is usually close to or slightly below PLA; flexible TPU typically needs a lower PA than PLA (it's too soft to sustain much compensation before it buckles in the extruder) - tune it separately rather than assuming a higher value.

Does PA change with nozzle size or temperature?

Yes - bigger nozzles and hotter prints flow more easily, lowering required PA. Re-tune when you change nozzle diameter, hotend (e.g. Volcano vs V6), or run a markedly different temperature.

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How This Calculator Works

Pressure Advance (Klipper) and Linear Advance (Marlin's M900) are the firmware features that compensate for the lag between the extruder commanding plastic and the molten polymer actually arriving at the nozzle. Without compensation, sharp corners bulge (pressure built up in the hotend keeps oozing) and the start of a line is under-extruded (pressure has not built yet). Tuning is empirical: print a tower or pattern that runs through a series of advance values (start → start + step × n), then pick the line where corners are sharpest and walls look most uniform. This calculator converts the line you picked (its zero-based index) plus the start value and step you used in your test back into the precise advance number to set permanently.

Formula / Method

Suggested advance = start + step × index, with index = 0 for the very first line printed. The corresponding firmware command is SET_PRESSURE_ADVANCE ADVANCE=value for Klipper or M900 K<value> for Marlin Linear Advance. Save it to your config: in Klipper's printer.cfg under [extruder] as pressure_advance: value; in Marlin's start G-code as the M900 line, or compile-time as LIN_ADVANCE_K. Typical settling values: 0.02–0.06 for direct-drive PLA, 0.30–0.80 for Bowden PLA, slightly higher for PETG, lower for TPU which is too soft for strong compensation.

Worked Example

You ran a Klipper pressure-advance tower starting at 0.000 with a step of 0.005 mm per line, 20 lines total. The 8th line (counting from zero) looks crispest at the corners and most uniform along the wall. Suggested advance = 0.000 + 0.005 × 8 = 0.040. The Klipper command is SET_PRESSURE_ADVANCE ADVANCE=0.0400; save by updating pressure_advance: 0.040 in printer.cfg and restarting. If your printer is Bowden with a long PTFE tube, the same tower with start 0.20 step 0.02 over 25 lines, best at line 15, gives 0.20 + 0.02 × 15 = 0.50 advance. If you ran this same tower test on Marlin instead, the command to save whatever best-line value you found would be M900 K<value> - but don't reuse the 0.50 Klipper number itself, since Klipper pressure_advance and Marlin's linear-advance K are not numerically interchangeable (see below).

Common Mistakes

Counting the lines from 1 instead of 0 - the first line on the tower is index 0; off-by-one undershoots.

Tuning with the wrong material - PETG, ABS, and TPU each need their own value; settle one and copy others using the same hotend.

Tuning at the wrong temperature or speed - advance interacts with melt viscosity; retune if you change temp by >15 °C or speed by >25%.

Picking a line by the corner only and ignoring under-extruded line starts (or vice versa) - the best line balances both.

Confusing Klipper's SET_PRESSURE_ADVANCE (volatile, lost on restart) with the printer.cfg entry (persistent).

Tips & FAQ

What range should I start with? Direct-drive: 0.00–0.10 in 0.005 steps. Bowden: 0.0–1.0 in 0.05 steps for a coarse pass, then 0.10 in 0.005 steps around the best zone. How tall should the tower be? 50–100 mm so you can see the result at print speed; the bottom layers run at a lower first-layer speed and are not representative. What about ringing / ghosting? That is input shaping, a separate tune (Klipper's SHAPER_CALIBRATE). PA does not fix it. One value for all filaments? No - PETG often wants 1.2–1.5× the PLA value, ABS slightly less than PLA. Does PA help on slow prints? Less - the lag is rate-dependent. PA matters most at >60 mm/s. Klipper vs Marlin number scale: Klipper's pressure_advance and Marlin's linear-advance K are computed differently and are not numerically interchangeable, even though both are entered in similar-looking units - always retune from scratch when switching firmware. How often to retune? After any major change - new hotend, new extruder, different brand of filament, new firmware. This is a derivation tool; the final test is always - does the corner look crisp?

Pressure Advance Calibration Calculator

Frequently Asked Questions

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