Volumetric Speed / Max Flow Calculator
Relate line width, layer height and print speed to volumetric flow (mm³/s), or solve for the maximum speed your hotend can sustain. Do this after e-steps and flow rate are dialled in.
This uses the common rectangular approximation: flow = line width × layer height × speed. Slicers such as PrusaSlicer and OrcaSlicer may model a rounded extrusion cross-section, so the slicer's reported flow can be a bit lower than this figure for the same settings. Estimates only — check against your slicer.
Formulas
Volumetric flow: mm³/s = line width (mm) × layer height (mm) × print speed (mm/s). Example: 0.42 × 0.20 × 100 = 8.4 mm³/s.
Max print speed: mm/s = max volumetric speed ÷ (line width × layer height). Example: limit 12 mm³/s with 0.42 × 0.20 → 12 ÷ 0.084 = 142.86 mm/s.
Another check: 0.6 mm line × 0.3 mm layer × 80 mm/s = 14.4 mm³/s.
Nozzle / layer height quick table (rules of thumb)
Typical layer-height range is about 0.25× to 0.75× nozzle diameter, and line width about 1.0× to 1.2× nozzle diameter. Prusa's Knowledge Base recommends keeping layer height to roughly 70–80% of nozzle diameter at most for good adhesion, and extrusion width around 110% of nozzle diameter.
| Nozzle | Layer height (≈0.25–0.75×) | Typical line width (≈1.0–1.2×) |
|---|---|---|
| 0.2 mm | 0.05–0.15 mm | 0.20–0.24 mm |
| 0.4 mm | 0.10–0.30 mm | 0.40–0.48 mm |
| 0.6 mm | 0.15–0.45 mm | 0.60–0.72 mm |
| 0.8 mm | 0.20–0.60 mm | 0.80–0.96 mm |
These are starting points, not hard limits. First layers are often thicker; vase-mode and high-flow setups can push beyond the table. Always check your slicer's max layer height for the selected nozzle.
How to find your hotend's real limit (OrcaSlicer)
- In OrcaSlicer open Calibration → Max Volumetric Speed (also called Max Flowrate).
- Use the defaults unless you already know a range: start 5 mm³/s, end 20 mm³/s, step 0.5. Slice and print the tower.
- Look for where layers start to fail or quality drops (a change from glossy to matte is a common cue). Measure the height just before defects begin.
- Limit = start + (height measured × step). Orca's own example: height 19 mm → 5 + (19 × 0.5) = 14.5 mm³/s. Or use Preview with the flow colour scheme and read the value at that layer.
- Enter the value under Filament settings → Max volumetric speed. Orca notes this test is a best-case scenario and recommends reducing the measured value by 10–20% (or more) for safer quality and to avoid clogs.
The limit depends on material, brand, colour, nozzle diameter and extruder — calibrate per filament rather than copying a number from someone else's printer. We do not list per-hotend figures here without a primary manufacturer source.
Sources
- OrcaSlicer Max Volumetric Speed calibration (defaults 5→20 mm³/s step 0.5, height formula, 10–20% derate): orcaslicer.com wiki – volumetric speed calibration (same content on the OrcaSlicer GitHub wiki).
- Where the setting lives: Material volumetric speed limitation (
filament_max_volumetric_speed). - Layer height ≤ ~70–80% of nozzle diameter and extrusion width ~110% of nozzle: Prusa Knowledge Base – Creating profiles for different nozzles. The 0.25× lower bound is a common fine-detail rule of thumb used with that upper bound.
Calibration chain: e-steps / rotation distance → flow rate → volumetric speed (this page).
FAQ
What is volumetric speed in 3D printing?
It is how many cubic millimetres of plastic the hotend melts and pushes per second (mm³/s). Print speed, line width and layer height all multiply into that figure, so a thick, wide, fast line needs a much higher flow than a fine slow one.
What is max volumetric speed in OrcaSlicer?
It is a filament setting (filament_max_volumetric_speed) that caps print speed so the requested flow never exceeds what the hotend can melt. Orca can calibrate it with a printed tower; enter the result under Filament → Max volumetric speed.
Why is the slicer flow a bit lower than this calculator?
This page uses the rectangular cross-section (width × height). Some slicers model rounded corners on the extrusion, which slightly reduces the area for the same nominal width and height, so their mm³/s can read a little lower.
What layer height should I use with a 0.4 mm nozzle?
A common rule of thumb is about 0.10–0.30 mm (0.25–0.75 × nozzle). Prusa recommends not exceeding roughly 70–80% of nozzle diameter for adhesion. Fine detail often uses the lower end; draft/speed prints the upper end.
Should I calibrate volumetric speed before or after flow rate?
After e-steps (or rotation_distance) and flow rate. Those fix how much filament is commanded; volumetric speed then limits how fast you can push that filament without under-extrusion or clogs.