Nozzle Flow Rate Calculator
Determine the maximum print speed your hotend can physically melt.
• Standard V6 / Ender 3: ~12-15 mm³/s
• Volcano / High Flow: ~20-30 mm³/s
• UHF / Rapido: ~45+ mm³/s
• Bambu Lab A1 / A1 mini: ~28 mm³/s
• Bambu Lab X1 / P1 series: ~32 mm³/s
• Bambu Lab H2D: ~40 mm³/s (High Flow hotend: ~65 mm³/s)
• Prusa MK4 / XL (Nextruder, standard nozzle): ~15-20 mm³/s
• Prusa MK4S / Core One, High Flow nozzle: ~24 mm³/s
Bambu figures are the maker's specs for ABS at 280 °C; expect less with PLA.
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What this calculator does
The Nozzle Flow Rate Calculator works out how much plastic your hotend has to melt each second (the volumetric flow) at your layer height, line width and speed. It compares that with your hotend's limit and tells you the fastest speed those settings allow.
How to use it
- Enter your layer height, line width and print speed from the slicer.
- Enter your hotend's maximum flow. The list on the page has typical figures for common printers.
- Read the flow, the gauge and the maximum speed. The gauge turns amber at 80% of your limit and red above it.
How it's calculated
Volumetric flow is the cross-section of one printed line times the speed. A printed line isn't a perfect rectangle: it has rounded sides. Slicers such as OrcaSlicer and PrusaSlicer model it as a rectangle with rounded ends, and this calculator uses the same formula so the numbers match:
area = layer height × (line width − layer height × (1 − π/4))
flow = area × speed
For a 0.2 mm layer and 0.4 mm line, the area is 0.0714 mm², so 60 mm/s needs about 4.28 mm³/s. (A plain rectangle would say 4.80, about 12% too high.) With a 15 mm³/s hotend, the top speed is 15 ÷ 0.0714 = 210 mm/s.
Why the limit matters
A hotend can only heat plastic so fast. Push past its limit and the plastic comes out too cold and too slowly: thin or missing lines, weak layers, a clicking or skipping extruder. Thicker layers and wider lines raise the flow quickly, so a 0.6 mm nozzle can hit the limit even at moderate speeds.
Finding your hotend's real limit
- Start with the maker's figure, as in the list on the page. Bambu Lab's figures are for ABS at 280 °C, so PLA usually manages less.
- Run a max flow test: OrcaSlicer has one under Calibration, "Max flowrate". It prints a strip at increasing flow and you note where it fails.
- Leave some headroom. Hotter printing raises the limit; cold filament, a worn nozzle or a fan blowing on the hotend lower it.
- Enter the result as the filament's "Max volumetric speed" in your slicer, and the slicer will slow down automatically wherever a move would exceed it.
Frequently asked questions
What line width should I use?
The one in your slicer's settings, usually a little wider than the nozzle (for example 0.42-0.45 mm on a 0.4 mm nozzle).
Does the max speed apply to every move?
It applies to moves that extrude with these settings. Walls, infill and first layers often use different widths, heights and speeds, so check each.
Sources: OrcaSlicer source code, Flow.cpp (line cross-section); Slic3r Manual, Flow Math; Bambu Lab and Prusa Research hotend specifications. Last reviewed on SuiteWebTools: October 2026.