3D Printing Calculators

FDM calibration & firmware

Maximum Volumetric Flow Rate Calculator

Hotends melt plastic at a limited cubic millimetres per second. This tool shows the flow your current profile asks for and the speed ceiling if you already know the hotend’s max flow.

Inputs

Units
mm
mm

Often 100–120% of nozzle diameter.

mm/s
mm³/s

Typical brass 0.4 mm: 8–15 mm³/s. High-flow CHT-style: 20–40+.

Results

Volumetric flow
5.04mm³/s
Max speed at this layer
142.9mm/s

Q_max divided by height × width.

Over hotend max?
No

Yes means this speed asks for more melt than the limit you entered.

The Result is indicative and educational. It does not constitute a design, a technical opinion or medical advice and does not replace calculations or verification by a person with the appropriate qualifications and authorisations. Before purchase, installation or use in practice – in particular in electrical installations – the Result should be verified by a qualified specialist. Details: Terms of Service, point 4.

Example products

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Calculation method

Volumetric flow Q = layer height × line width × print speed. All three are millimetres and millimetres per second, so Q is mm³/s. Maximum speed at that layer is the hotend’s max flow divided by (height × width). The over-max flag is 1 when Q exceeds the entered limit. Imperial converts mm to inches and mm/s to in/s and mm³/s to in³/s; the physics is unchanged.

Exact formula

Q = h × w × v with h and w in millimetres and v in mm/s, so Q is mm³/s. v_max = Q_max / (h × w). Over-max is true when Q > Q_max. Limits: Q uses a rectangle h×w, not the true stadium extrusion. Max flow is the number you typed, not a measured melt test.

Temperature is part of max flow

Hotter plastic flows easier until it degrades. A number from 250 °C PETG does not apply to 200 °C PLA.

Acceleration still matters

Short segments never reach the speed you typed. Volumetric flow on tiny infill is lower than the profile’s headline mm/s.

Frequently asked questions

What max flow should I type?

Measure it: increase speed on a single-wall cube until extrusion starves, then compute Q at that speed. Vendor charts are a starting guess.

Does 0.6 mm nozzle change the formula?

The formula is the same. Line width and max flow both go up, so v_max may or may not rise.

Why not 100% of nozzle as line width?

Many profiles use ~105–120% for bonding. Wider lines raise Q at the same speed.

Is this the same as slicer flow %?

No. Slicer flow scales extrusion multiplier. This Q is geometric: height × width × speed.

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