How to use
- Choose flow from speed or speed from a known flow limit. Enter line width and layer height for the extrusion being evaluated.
- Choose the rounded stadium cross-section or the separate rectangular approximation.
- Enter line speed, or provide a positive tested hotend flow limit when solving for speed. A limit is optional when only calculating required flow.
- Compare demand with the supplied limit and check the assumptions before changing a slicer profile.
Calculation method
Flow Q equals deposited cross-sectional area A multiplied by line speed v. The stadium model uses A = h(w − h) + πh²/4 and requires width w at least height h. Rectangular approximation uses A = wh. Speed from a supplied flow limit is v = Qlimit / A. Dimensions in millimetres give area in mm²; speed in mm/s gives flow in mm³/s. The result describes nominal ordinary extrusion at 100% flow.
Worked example
At width 0.45 mm, height 0.20 mm and 60 mm/s, stadium area is approximately 0.08141593 mm² and flow is 4.88495559 mm³/s. A user-supplied 12 mm³/s limit corresponds to approximately 147.3913 mm/s at that same section. The rectangular approximation would give 0.09 mm² and 5.4 mm³/s at 60 mm/s.
Assumptions and limits
A flow-derived speed is a throughput ceiling, not a guarantee of attainable or good-quality printing. It does not include acceleration, cooling, bridging, motion-system limits, special line types or material changes. The hotend limit must be established for the actual material, temperature and equipment; the tool deliberately does not supply a universal limit.
Continue your plan
Use the extruder calibration calculator for measured feed correction, the printing cost calculator for job costs, or the filament calculator for available material.
Copy, download or print a valid result to keep the inputs with the estimate. Currency selections label your prices; they do not apply an exchange rate. Product-dependent examples should be replaced with data for the material or equipment you actually use.
For the measurement and planning details, read connecting fdm line width, layer height and volumetric flow.