Rotation Distance Calculator – Klipper

What is Rotation Distance?

Rotation distance defines how far an axis moves with one complete revolution of the stepper motor. Unlike steps per millimeter (steps/mm) used in Marlin and RepRap firmware, rotation_distance focuses on physical measurements rather than electronic step counts. This makes Klipper configuration more intuitive and directly tied to your printer’s hardware specifications.

If you’re migrating from Marlin, think of rotation_distance as representing the physical distance traveled per motor rotation, while steps/mm represents the number of electronic pulses needed to move one millimeter. Both achieve the same goal through different approaches.

The official Klipper documentation provides additional technical details on rotation distance implementation.

Standard Values by Hardware Type

Belt-Driven Axes (X/Y)

Belt-driven systems use a simple formula: belt pitch multiplied by pulley teeth count. GT2 belts with 2mm pitch dominate consumer 3D printing. Common configurations:

Most consumer printers (Ender series, Prusa i3, Voron) use 20-tooth pulleys. Delta printers often use 16-tooth pulleys for their XYZ carriages. To verify your configuration, count the teeth on the pulley attached directly to your stepper motor shaft.

Do not calibrate X/Y axes by measuring printed objects. Filament shrinkage, model tolerances, and other factors introduce more error than they solve. Calculate from hardware specifications instead.

Leadscrew-Driven Axes (Z)

Leadscrews use thread pitch multiplied by the number of independent thread starts. The “T8” designation indicates an 8mm diameter screw with specific thread characteristics:

T8×8 leadscrews appear on most consumer printers including Ender 3, CR-10, and similar machines. Prusa i3 printers use T8×2 leadscrews for finer Z-axis resolution. If your calculation yields unusual values like 7.89mm or 3.14mm, verify your leadscrew specifications.

Extruders

Extruder rotation distance varies significantly based on drive gear diameter and gear ratios. Starting values for common extruders:

These values serve as starting points only. Extruders require calibration through physical measurement due to variations in filament grip, drive gear wear, and tension settings.

Calibration Methods

Belt Systems: Calculate from Hardware

For belt-driven axes, hardware calculation provides accuracy exceeding measurement methods:

1. Identify belt type (check manufacturer specifications or measure tooth spacing with calipers – GT2 belts have 2mm spacing)
2. Count teeth on motor pulley (remove belt and count manually if needed)
3. Multiply belt pitch by tooth count (2mm × 20 teeth = 40mm)
4. Enter this value in your [stepper_x] and [stepper_y] config sections

Belt-driven systems achieve consistent results through hardware calculation because belts don’t stretch significantly under normal operating tension, and pulley teeth engage predictably with belt teeth.

Leadscrews: Identify Specifications

Leadscrew rotation distance comes from physical thread geometry:

1. Check your printer’s documentation or leadscrew markings for type (T8×8, T8×2, etc.)
2. Determine thread pitch (distance between adjacent threads – usually 2mm for T8 screws)
3. Count thread starts (how many independent helical threads run along the screw – T8×8 has 4, T8×2 has 1)
4. Multiply pitch by starts (2mm × 4 = 8mm for T8×8)

Common Z-axis values are whole numbers. Unusual calculations like 7.89mm or 3.7mm indicate incorrect specifications or non-standard hardware.

Extruders: Physical Measurement

Extruder calibration requires the “measure and trim” procedure for accuracy:

1. Find your current rotation_distance in printer.cfg under [extruder]
2. Heat hotend to normal printing temperature for your filament
3. Mark filament with permanent marker at exactly 120mm from extruder entry point (use calipers for precision)
4. Execute commands: G91 then G1 E100 F60
5. Wait for extrusion to complete (approximately 100 seconds at F60 feed rate)
6. Measure new distance from mark to extruder with calipers
7. Calculate actual extrusion: 120mm – measured_distance
8. Calculate new rotation_distance: current_value × (100 ÷ actual_extrusion)

The slow extrusion rate (F60 = 1mm/second) prevents pressure buildup in the hotend that would cause the extruder to skip or over-extrude. Fast extrusion rates produce inaccurate calibration values.

Run this calibration 2-3 times and average the results for best accuracy. If successive measurements vary by more than 2mm, check for mechanical issues like loose grub screws, worn drive gears, or inconsistent filament grip.

Geared Extruders

Geared extruders like Bondtech BMG or E3D Titan use gear reduction to increase torque. Klipper supports two configuration approaches:

Option 1: Effective rotation distance
Set rotation_distance to the final effective value accounting for gear reduction:

[extruder]
rotation_distance: 7.7
microsteps: 16

Option 2: Document gear ratio explicitly
Set rotation_distance to theoretical drive gear circumference and specify gear_ratio separately:

[extruder]
rotation_distance: 22.0
gear_ratio: 50:17
microsteps: 16

Both methods produce identical results. Option 2 provides clearer documentation of your hardware configuration and simplifies future modifications if you change drive gear diameter while keeping the same gear ratio.

For Bondtech BMG clones, the 50:17 gear ratio (approximately 2.94:1) remains standard across manufacturers. E3D Titan uses exactly 3:1 (3 full rotations of the motor produce 1 rotation of the drive gear).

Motor and Microstepping Changes

Rotation distance remains constant when changing motor types or microstepping settings. These parameters affect electronic step generation, not physical distances traveled.

When switching from 1.8° to 0.9° stepper motor:

# Before (1.8° motor - 200 steps/revolution)
[stepper_x]
rotation_distance: 40
microsteps: 16
# full_steps_per_rotation: 200  (default, not shown)

# After (0.9° motor - 400 steps/revolution)
[stepper_x]
rotation_distance: 40  # Unchanged
microsteps: 16
full_steps_per_rotation: 400  # Add this line

When changing microstepping from 16 to 32:

# Before
[stepper_x]
rotation_distance: 40
microsteps: 16

# After
[stepper_x]
rotation_distance: 40  # Unchanged
microsteps: 32  # Only this changes

Klipper automatically recalculates internal step generation based on these parameters combined with rotation_distance. You don’t perform manual conversions.

Dimensional Accuracy Issues

If prints show dimensional problems after correctly setting rotation_distance, the issue lies elsewhere in your system.

X/Y dimensional errors: Check belt tension (should deflect 5-10mm under moderate finger pressure), verify pulley grub screws are tight against motor shaft flats, inspect for bearing play in linear rails or wheels, and confirm CoreXY belt paths if applicable.

Z height problems: Verify Z endstop trigger point, check first layer height settings in slicer, confirm bed leveling across the entire surface, and inspect leadscrew coupling for looseness or misalignment.

Extrusion inconsistencies: Confirm filament diameter in slicer matches actual filament (measure with calipers in 3-5 locations and average), verify nozzle size configuration matches installed nozzle, calibrate flow rate separately from rotation_distance, and ensure nozzle temperature is appropriate for your filament.

Rotation distance is a physical hardware property. If mechanical systems are sound and belts aren’t slipping, calculated values should be correct. Don’t adjust rotation_distance to compensate for mechanical problems or slicer settings.

Common Printer Configurations

Crealty Ender 3 Series

[stepper_x]
rotation_distance: 40.0
microsteps: 16

[stepper_y]
rotation_distance: 40.0
microsteps: 16

[stepper_z]
rotation_distance: 8.0
microsteps: 16

[extruder]
rotation_distance: 34.2  # Calibrate with measurement method
microsteps: 16

Prusa i3 MK3S

[stepper_x]
rotation_distance: 40.0
microsteps: 16

[stepper_y]
rotation_distance: 40.0
microsteps: 16

[stepper_z]
rotation_distance: 8.0
microsteps: 16

[extruder]
rotation_distance: 7.7  # BMG-style extruder
microsteps: 16

Voron 2.4 (CoreXY)

[stepper_x]
rotation_distance: 40.0
microsteps: 16

[stepper_y]
rotation_distance: 40.0
microsteps: 16

[stepper_z]
rotation_distance: 8.0
microsteps: 16

[extruder]
rotation_distance: 22.678
gear_ratio: 50:17
microsteps: 16

These examples use standard hardware. Your specific printer may vary if you’ve modified pulleys, belts, leadscrews, or extruders. Always verify against your actual hardware specifications.

The Klipper configuration reference provides complete details on all stepper motor parameters and options for advanced configurations.