3D Printing guide
Flow Rate Calculator Guide
This page holds the detailed reference that supports the focused interactive tool.
Open the Flow Rate CalculatorHow to Use This Calculator
- Print a single-wall calibration object with one perimeter, no top or bottom layers, and 0% infill.
- Choose one clean reading for a quick check or average three readings to reduce local measurement error.
- Enter the current profile flow, expected line width, and measured wall thickness values.
- Apply the corrected percentage or extrusion multiplier to this material profile, then print the same test again to confirm.
Inputs and Assumptions
| Current flow | Use the value currently saved in this filament or material profile. |
|---|---|
| Expected wall thickness | Use the line width expected from the single-wall test, not automatically the nozzle diameter. |
| Wall measurement 1 | Measure away from the seam and first layers. |
| Wall measurement 2 | Used in the three-reading average mode. |
| Wall measurement 3 | Used in the three-reading average mode. |
Three-reading flow calibration example
A 100% profile with a 0.45 mm target and wall readings of 0.47, 0.46, and 0.45 mm has a 0.46 mm average. The corrected result is 97.83%, or a 0.9783 extrusion multiplier. Reprint before treating that value as final.
Calibrate Extruder Motion First
E-steps and rotation_distance make the extruder push the commanded filament length. Flow rate, also called flow ratio or extrusion multiplier, fine-tunes the material profile after that motion is accurate.
If a 100 mm extrusion test is still wrong, correct the firmware value before changing flow. Otherwise the material profile only masks the mechanical calibration error.
Printing a Reliable Single-Wall Test
- Use one perimeter, zero top and bottom layers, and 0% infill so only the outer wall is measured.
- Use the same nozzle, temperature, speed, line width, and material profile that the correction will be applied to.
- Confirm in the slicer preview that the test wall keeps a constant line width; variable-width perimeter generation can invalidate the expected measurement.
- Disable ironing, extra perimeters, and seam-gap features that change the test wall.
- Measure away from the seam, corners, blobs, and first few layers. Use light, repeatable caliper pressure.
One Reading or Three
One clean reading is enough for a quick check. Three readings are safer when the wall varies slightly by height or caliper placement.
The calculator ignores the extra readings in single-reading mode. In average mode it uses all three values before calculating the correction.
After a Material or Nozzle Change
A new material can need its own flow ratio, temperature, retraction, and pressure-advance values. Stringing alone does not prove that flow is wrong; dry the filament and tune temperature and retraction separately.
After changing a nozzle or hotend, confirm the installed nozzle size, slicer line width, Z offset, and heater behavior before running the wall test. A large correction is a reason to check the setup, not a value to accept blindly.
The Flow Formula
Corrected flow = current flow x expected wall thickness / average measured wall thickness. Divide the corrected percentage by 100 to get the extrusion multiplier or flow ratio.
A wall that is thicker than expected lowers the result. A thinner wall raises it. The adjustment shown is the difference from the current profile in percentage points.
After Flow: Pressure Advance and Speed
Once flow is confirmed, tune pressure advance or linear advance for corner behavior. Then check that the requested speed stays below the hotend's tested volumetric-flow limit.
Flow ratio and volumetric flow are different. One corrects the material profile; the other describes how much plastic the hotend must melt each second.
Formula
Corrected flow % = current flow % x expected wall thickness / average measured wall thickness. Extrusion multiplier = corrected flow % / 100.
Limits of This Calculator
- Calibrate E-steps or rotation_distance first. Flow should not hide an incorrect commanded filament length.
- Do not use flow alone to fix first-layer Z offset, wet filament, stringing, a partial clog, or a slicer line-width mismatch.
- Flow is material-profile specific. PLA, PETG, TPU, filled filaments, and different spools can need different values.
- A corrected wall does not guarantee part dimensions. Use slicer XY compensation for repeatable geometry errors after extrusion is calibrated.
FAQ
Should flow replace E-step calibration?
No. E-steps or rotation distance and flow are separate calibration layers.
Can I use this for any slicer?
Yes. Use the percentage result in slicers such as Cura. Use the decimal extrusion multiplier in PrusaSlicer, OrcaSlicer, Bambu Studio, or another slicer that uses a flow ratio.
What flow or extrusion multiplier should I start at?
Start at 100% (a multiplier of 1.0), print a single-wall test, then correct based on the measured wall thickness. Most well-calibrated printers end up within a few percent of 100%.
How many walls should the flow test object have?
Use a single perimeter with no top or bottom layers and 0% infill, so the calipers measure only one extruded wall.
Should I use one wall measurement or average three?
One clean reading is useful for a quick check. Averaging three readings taken away from the seam and first layers reduces the effect of a local bump, gap, or caliper placement error.
Why is my calculated flow far from 100%?
A large correction usually points to uncalibrated E-steps or rotation_distance, a wrong line width or nozzle size, a loose or partial clog, or a measurement error. Check those first because flow is a fine-tuning step.