Retraction Distance Calculator
Retraction distance controls how much filament your extruder pulls back during non-printing travel moves to stop oozing and stringing. The right value depends mainly on whether you run a direct-drive or Bowden setup, and on the length of the filament path. This calculator gives a sensible starting distance from your base value and tube length, which you then confirm and refine with a retraction test print. There is no universal correct number; the goal is the smallest distance that eliminates stringing.
Retraction distance formula
Suggested distance = base + (tube length / 100) * allowance per 100 mm
Direct-drive printers use a tube length of 0, so the suggestion equals the base. Bowden printers add a small amount proportional to tube length, reflecting the extra filament path that stores pressure. Always finish by running a retraction tuning print.
Worked example
A Bowden printer has a base of 1 mm and a 400 mm PTFE tube, with an allowance of 1 mm per 100 mm. Suggested distance = 1 + (400 / 100) * 1 = 1 + 4 = 5.00 mm. This is a typical Bowden starting figure; reduce it if you see gaps or grinding.
Retraction distance: frequently asked questions
What retraction distance should I start with?
Retraction distance is the length of filament the extruder pulls back to relieve pressure during travel moves. Direct-drive extruders need only a short pull because the filament path is short, commonly 0.5 to 2 mm. Bowden setups need more because the filament must compress through a long tube, commonly 3 to 7 mm. These are starting points; the correct value is found by printing a test and reducing stringing.
How does this calculator suggest a distance?
It takes your base distance for the extruder type plus an adjustment for the PTFE or Bowden tube length, since a longer path stores more pressure and needs a slightly larger pull. The output is a suggested starting distance, not a guaranteed value. Always confirm with a retraction tower or stringing test.
Does retraction distance differ by material?
Yes. Flexible filaments such as TPU need very little or no retraction because they compress and buckle. PLA and PETG tolerate retraction well. Because the ideal depends on material, hardware, and temperature, treat the calculated figure as a tuning start and adjust from observed stringing.
Can too much retraction cause problems?
Yes. Excessive retraction can grind filament, cause gaps at the start of extrusion, or clog the hotend by pulling molten material into the cold zone. Increase distance in small steps only until stringing stops, then leave it there.
Sources and method
- The suggested distance is a linear tuning heuristic based on extruder path length; it is a starting point only, confirmed by a physical retraction test print.
- National Institute of Standards and Technology: Additive manufacturing research.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.