Calibration Calculators
Retraction Calculator
Turn a retraction tuning tower into a final retraction distance by entering the start distance, the distance added per mm of height, and the height where stringing stops, and see the retracted filament volume.
Quick answer
To set retraction distance from a tuning tower, multiply the height where stringing stops by the distance added per mm, then add the start distance. For example, 0 + 20 × 0.1 = 2 mm. Direct-drive extruders usually need 0.5–2 mm and Bowden setups 3–7 mm.
Results update below from browser-local calculations.
Breakdown
| Retraction distance | 0 |
|---|---|
| Retracted filament volume | 0 |
How to Use This Calculator
- Print a retraction tuning tower that increases the retraction distance with height, for example with Klipper TUNING_TOWER on the retract distance or a slicer retraction pattern.
- Enter the start distance and the distance added per mm that you used, then measure the lowest Z height where stringing disappears cleanly.
- Apply the resulting retraction distance in your slicer or firmware, then reprint a quick stringing test such as two towers to confirm.
Inputs and Assumptions
| Tower start distance | The retraction distance at the bottom of the tuning tower. |
|---|---|
| Distance added per mm | How much retraction distance increases per mm of tower height. |
| Height where stringing stops | Measure the Z height where the strings first disappear cleanly. |
| Filament diameter | Used to estimate the retracted filament volume. |
Retraction tower example
If the tower started at 0 mm, added 0.1 mm per mm of height, and stringing stopped at 20 mm, the retraction distance is 0 + 20 × 0.1 = 2 mm. For 1.75 mm filament that pulls back about 4.81 mm³ of melt each retraction.
Direct Drive vs Bowden Retraction
- Direct-drive extruders keep the filament close to the nozzle and usually need roughly 0.5 to 2 mm.
- Bowden setups must pull through a long tube and often need roughly 3 to 7 mm.
- Longer or softer Bowden tubes need more distance; stiff tubes and short paths need less.
- Flexible filament such as TPU needs very short, slow retractions or none at all.
Distance vs Retracted Volume
Retraction distance is how far the extruder pulls the filament back. Retracted volume is how much melt that represents, which depends on filament diameter.
Comparing volume is useful when you switch between 1.75 mm and 2.85 mm filament, because the same distance moves more than two and a half times as much material at 2.85 mm.
Reduce Stringing Beyond Retraction
- Dry the filament; wet filament strings no matter how much you retract.
- Lower the nozzle temperature in small steps to reduce oozing.
- Raise travel speed so the nozzle spends less time over gaps.
- Enable wipe or coasting in the slicer for stubborn materials.
Where Retraction Fits in Calibration
Tune extruder steps and flow rate first, then pressure advance for corners, then retraction for travel moves. Doing it in this order keeps each test meaningful.
Formula
Retraction distance = tower start distance + measured height × distance added per mm. Retracted filament volume = π × (filament diameter / 2)² × retraction distance.
Limits of This Calculator
- Retraction removes stringing, not under- or over-extrusion. Calibrate extruder steps and flow first.
- Too much retraction can cause clogs, filament grinding, or gaps at the start of lines, so use the lowest distance that works.
- Temperature, travel speed, and filament moisture also affect stringing, so tune them alongside retraction.
FAQ
What is a good starting retraction distance?
Direct-drive extruders often work well between roughly 0.5 and 2 mm, while Bowden setups often need 3 to 7 mm depending on tube length. Always confirm with a retraction tower instead of trusting a default.
How do I run a retraction tower?
Print a tall two-pillar or single-tower test that increases the retraction distance with height, find the lowest height where stringing disappears, and enter that height with the start distance and factor you used.
Why does the calculator show retracted volume?
Retracted volume is the melt the extruder pulls back each retraction. Comparing volume rather than distance helps when you switch between 1.75 mm and 2.85 mm filament.
Will more retraction always remove stringing?
No. Too much retraction can cause clogs, grinding, or gaps. Tune temperature and travel speed as well, and use the lowest distance that removes stringing.