klipper rotation distance calculator

Calculate and calibrate the `rotation_distance` for your 3D printer’s axes and extruder with precision.

Two Ways to Calculate

Fine-Tuning Calibration Calculator

Use this for calibrating any axis or extruder by measuring actual movement.

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Initial Hardware Setup Calculator

Get a baseline `rotation_distance` based on your printer’s hardware.

What is Klipper Rotation Distance?

In the Klipper 3D printing firmware, the `rotation_distance` is a critical configuration parameter that defines how far an axis moves for one full rotation of its stepper motor. Unlike the “steps_per_mm” value used in firmwares like Marlin, `rotation_distance` is based on the physical properties of your hardware, making it a more intuitive and direct way to configure your printer’s motion system. Getting this value right is fundamental for dimensional accuracy in your prints. An incorrect `rotation_distance` will cause your printer to either over-extrude/over-move or under-extrude/under-move, leading to parts that are the wrong size.

This klipper rotation distance calculator helps both in establishing an initial value based on your hardware and, more importantly, in fine-tuning that value through a precise calibration process. Every Klipper user, from hobbyist to professional, must understand and correctly set this value to achieve high-quality prints.

`rotation_distance` Formulas and Explanation

The calculation for `rotation_distance` depends on the mechanical system driving the axis. Below are the primary formulas used by our klipper rotation distance calculator.

For Belt-Driven Axes (like X and Y)

rotation_distance = belt_pitch * pulley_tooth_count

This is the most straightforward calculation. It simply multiplies the distance between belt teeth by the number of teeth on the motor’s pulley to find the total distance traveled in one motor revolution.

For Lead Screw-Driven Axes (like Z)

rotation_distance = screw_pitch * number_of_starts

For lead screws, the distance is the pitch (the distance a nut moves per revolution for a single-start screw) multiplied by the number of independent threads (starts) on the screw. A common T8 lead screw has a 2mm pitch and 4 starts, resulting in an 8mm rotation distance.

For Calibration (Any Axis or Extruder)

new_rotation_distance = current_rotation_distance * (actual_measured_distance / requested_distance)

This is the universally applicable calibration formula. It adjusts your current `rotation_distance` based on the real-world performance of your printer, correcting any inaccuracies from mechanical or material variables.

Variables Table

Description of variables used in rotation distance calculations.

Variable	Meaning	Unit	Typical Range
belt_pitch	Distance between consecutive teeth on the timing belt.	mm	2 (for GT2), 3 (for GT3)
pulley_tooth_count	Number of teeth on the pulley attached to the stepper motor.	–	16 – 40
screw_pitch	Distance a nut travels per single revolution on a single-start screw.	mm	1 – 8
number_of_starts	Number of independent threads on the lead screw.	–	1, 2, 4
requested_distance	The target distance commanded via G-code.	mm	50 – 100
actual_measured_distance	The real distance measured with calipers after the move.	mm	Varies based on accuracy

Practical Examples

Example 1: Initial Setup for a CoreXY Y-Axis

You are building a new Voron 3D printer which uses a GT2 belt (2mm pitch) and a 20-tooth pulley on the Y-axis stepper motor.

• Inputs:
  • Drive System: Belt
  • Belt Pitch: 2 mm
  • Pulley Tooth Count: 20
• Calculation: 2 * 20 = 40
• Result: Your initial `rotation_distance` for the Y-axis is 40.

Example 2: Calibrating an Under-Extruding Extruder

You notice your prints are weak and have gaps, a sign of under-extrusion. Your `printer.cfg` currently has a `rotation_distance` of 33.5 for the extruder. You perform a calibration test.

• Inputs:
  • Current `rotation_distance`: 33.5
  • Requested Extrusion Length: 100 mm
  • Actual Measured Extrusion: 96 mm
• Calculation: 33.5 * (96 / 100) = 33.5 * 0.96 = 32.16
• Result: Your new, more accurate `rotation_distance` is 32.16. This smaller value means the motor will need to turn more to extrude the same amount of filament, correcting the under-extrusion.

How to Use This klipper rotation distance calculator

Using this calculator is a simple, two-stage process: getting a baseline and then fine-tuning it.

1. Initial Setup (Optional but Recommended): If you’re setting up a new printer or axis, use the “Initial Hardware Setup Calculator”. Select your drive system (belt or lead screw) and enter the physical specifications of your components. This gives you a solid starting point for your `printer.cfg` file.
2. Fine-Tuning Calibration (Essential): This is the most important step for accuracy.
   • Enter your current `rotation_distance` from your `printer.cfg` file into the “Fine-Tuning” calculator.
   • Heat up your hotend to a normal printing temperature.
   • Carefully mark your filament about 120mm before it enters the extruder.
   • Use your printer’s interface to slowly extrude 100mm of filament (e.g., `G1 E100 F60`).
   • Measure the remaining distance from the extruder body to your mark. Subtract this from your initial mark (e.g., 120mm – 22mm = 98mm actual extrusion).
   • Enter the requested (100mm) and actual measured distances into the calculator.
3. Interpret Results: The calculator provides the new `rotation_distance`. The primary result is the value you need. The intermediate values help you understand the degree of error that was corrected.
4. Update Configuration: Copy the new value and update the `rotation_distance` in the relevant stepper section of your `printer.cfg` file, then restart Klipper.

Key Factors That Affect `rotation_distance`

While the hardware formulas provide a great start, several factors can influence the true `rotation_distance`, which is why calibration is essential.

• Stepper Motor Type: Most motors are 1.8° (200 steps/rotation), but 0.9° motors (400 steps/rotation) exist and affect the underlying step calculations that Klipper performs.
• Microstepping Level: Set in your driver configuration (e.g., 16, 32, 64), microstepping affects smoothness but not the `rotation_distance` calculation itself, as Klipper abstracts this away.
• Extruder Gear Ratio: Geared extruders (like a BMG or Sherpa Mini) have a gear ratio (e.g., `50:17`) that must be set in the `[extruder]` config section. The `rotation_distance` is then calculated based on the extruder gear itself, not the motor.
• Belt Tension: A loose belt can slip or not engage the pulley teeth perfectly, leading to a discrepancy between the calculated and actual travel distance.
• Filament Properties: A soft filament might get “squished” more by the extruder hobb, slightly changing the effective diameter and thus the amount of filament pushed per rotation.
• Mechanical Wear: Over time, wear on belts, pulleys, or extruder gears can subtly alter the motion system’s behavior, making periodic recalibration a good practice.

Frequently Asked Questions (FAQ)

Why does Klipper use `rotation_distance` instead of steps/mm?

Klipper uses `rotation_distance` because it ties configuration directly to the physical, measurable hardware of the printer (like belt pitch and pulley size), which is often more intuitive than calculating an abstract steps-per-millimeter value.

How often should I calibrate my `rotation_distance`?

You should always calibrate it when you first set up the printer, or after changing any major mechanical component on an axis (new motor, belt, pulley, or extruder). It’s also good practice to re-check extruder calibration when you switch to a very different type of filament (e.g., from PLA to flexible TPU).

What is `full_steps_per_rotation`?

This is a Klipper setting derived from your stepper motor’s step angle. For a standard 1.8-degree motor, it’s 200 (360 / 1.8). For a 0.9-degree motor, it’s 400. You typically don’t need to change this unless you have a non-standard motor.

My Z-axis `rotation_distance` from the formula is not a whole number. Is that okay?

For lead screws, it is very common for the `rotation_distance` to be a whole number (like 8 for a T8 screw). If your calculation for a belt-driven axis is very close to a whole number (e.g., 39.99), the Klipper documentation recommends rounding it.

Can I use this calculator for my extruder?

Yes. The “Fine-Tuning Calibration” calculator is the perfect tool for extruder calibration. The initial setup for an extruder is more complex due to gear ratios and hobb diameter, so the empirical measure-and-trim method is always recommended.

Why do I need to extrude slowly during the test?

Extruding slowly (e.g., at 1-2mm/s) prevents high pressure from building up in the hotend, which could cause filament slippage or extruder motor skipping, leading to an inaccurate measurement.

What’s the difference between `rotation_distance` and `gear_ratio`?

`gear_ratio` is a separate Klipper parameter used specifically for geared systems (like many extruders). You define the gear ratio, and then the `rotation_distance` is calculated based on the final driven gear, not the motor shaft.

The calculator gave me a new value. What now?

Open your `printer.cfg` file, find the section for the axis or extruder you calibrated (e.g., `[stepper_x]` or `[extruder]`), replace the old `rotation_distance` value with the new one, save the file, and restart Klipper from your web interface.