Nozzle Flow Rate Calculator
The Number That Actually Limits Your Print Speed
Every hotend has a maximum volumetric flow rate — the fastest rate at which it can melt and push out filament before under-extrusion sets in — and it's usually the real ceiling on print speed, not the stepper motors or the frame's rigidity. Slicers let you set layer height and speed independently, but multiplying them together against nozzle diameter shows whether the combination is actually achievable on your hardware.
The Formula
This gives volumetric flow rate in mm³ per second, which the calculator also converts to mm³ and cm³ per minute. If a material density is supplied, it additionally computes mass flow rate in grams per minute.
Where This Calculation Matters
- Checking a speed setting against hotend limits — standard brass nozzles on all-metal hotends typically max out around 10–15 mm³/s for PLA; exceeding it causes skipped steps and gaps in the extrusion.
- Tuning for a new nozzle size — a 0.6mm or 0.8mm nozzle allows proportionally higher flow at the same speed, letting print speed or layer height increase without exceeding the hotend's melt rate.
- Diagnosing under-extrusion — if a print shows thin or missing extrusion at higher speeds, comparing the requested flow rate against the hotend's rated maximum usually explains it.
- High-flow hotend upgrades — volcano-style or high-flow hotends are rated for flow well above stock hotends, and this calculator quantifies exactly how much speed headroom that buys.
Flow Rate by Layer Height and Speed (0.4mm nozzle)
| Layer height | 40 mm/s | 60 mm/s |
|---|---|---|
| 0.10 mm | 1.6 mm³/s | 2.4 mm³/s |
| 0.15 mm | 2.4 mm³/s | 3.6 mm³/s |
| 0.20 mm | 3.2 mm³/s | 4.8 mm³/s |
| 0.28 mm | 4.48 mm³/s | 6.72 mm³/s |
| 0.32 mm | 5.12 mm³/s | 7.68 mm³/s |
Rated maximum flow varies by hotend design — check your hotend manufacturer's specification rather than assuming a single figure applies universally.
How to Use This Calculator
- Enter the nozzle diameter in millimeters.
- Enter the layer height in millimeters.
- Enter the print speed in mm/s.
- Optionally enter material density in g/cm³ to also get mass flow rate in grams per minute.
- Select Calculate to get the volumetric flow rate.
Related Calculations
Cross-check a candidate layer height against your nozzle with the Layer Height Calculator, then estimate the resulting duration with the Print Time Estimator.