Flow & Nozzle Calculators
Flow Rate Calculator
Calculate a corrected slicer flow rate or extrusion multiplier from a single-wall measurement to fix over- or under-extrusion per filament.
Quick answer
To correct slicer flow rate, multiply your current flow by the expected wall thickness divided by the measured wall thickness. For example, 100% × 0.45 ÷ 0.48 ≈ 93.75%. Print a single-wall test, measure the wall with calipers, then apply the new flow or extrusion multiplier per filament.
Results update below from browser-local calculations.
Breakdown
| New flow | 0 |
|---|
How to Use This Calculator
- Print a single-wall calibration object (often called a flow or extrusion-multiplier cube) with one perimeter and no top or bottom layers.
- Enter your slicer's current flow or extrusion multiplier, the expected wall width (your line width or nozzle setting), and the measured wall thickness from calipers.
- Apply the new flow percentage in your slicer's filament or material settings, then reprint the test to confirm.
Inputs and Assumptions
| Expected wall thickness | Enter this value in mm. |
|---|---|
| Measured wall thickness | Enter this value in mm. |
| Current flow | Enter this value in %. |
Flow and extrusion-multiplier example
If your current flow is 100%, the expected wall is 0.45 mm, and calipers read 0.47 mm, the corrected flow is about 95.7%. Thicker-than-expected walls mean over-extrusion, so flow comes down.
Why Calibrate Flow Separately
E-steps and rotation_distance make the extruder push the commanded length of filament. Flow rate, also called the extrusion multiplier, fine-tunes how much plastic actually ends up in the wall after squish, pressure, and slight filament diameter variation.
Because it depends on the material and even the individual spool, flow is tuned per filament in the slicer rather than in firmware.
Printing a Reliable Single-Wall Test
- Use one perimeter, zero top and bottom layers, and 0% infill so only the outer wall is measured.
- Disable ironing, extra perimeters, or seam-gap features that change wall width.
- Measure the wall at three or four heights with calipers and average the readings.
- Avoid the seam and the first few layers, which are not representative.
The Flow Formula
New flow = current flow x expected wall width / measured wall width. If the measured wall is thicker than expected you are over-extruding and flow decreases; if it is thinner, flow increases.
Keep corrections small. A result far from 100% usually means E-steps, line width, or filament diameter is wrong, not flow.
After Flow: Pressure Advance and Speed
Once flow is dialed in, tune pressure advance (Klipper) or linear advance (Marlin) for corner quality, then confirm your speeds stay under the hotend's volumetric flow limit.
Use the volumetric flow and nozzle speed calculators to check that fast prints are not starved for plastic.
Formula
New flow % = current flow % × expected wall thickness / measured wall thickness.
Limits of This Calculator
- Calibrate E-steps or rotation_distance first; flow only fine-tunes an already-accurate extrusion amount.
- Measure several spots on the wall and average them, because a single reading can be skewed by a blob or gap.
- Flow is filament-specific. PETG, PLA, and TPU often need different multipliers even on the same printer.
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, if your slicer supports a flow or extrusion multiplier percentage.
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.
Why is my calculated flow far from 100%?
A flow value far from 100% usually points to uncalibrated E-steps or rotation_distance, a wrong line width, or incorrect filament diameter. Fix those first, because flow is only a small fine-tuning step.