Volumetric Flow Rate Calculator for 3D Printing
Enter the layer height, line width and speed to see the flow in mm³/s, how close it is to your hotend limit and the fastest speed that stays within it.
Your measurements
Enter the layer height, line width and speed, and pick your hotend's limit or type your own. Everything updates as you type.
The line
Often a little wider than the nozzle.
The speed of the feature you are checking, such as infill or outer walls.
Hotend and filament
The presets are typical ballpark values for PLA, not measurements of any product. Test your own with a max-flow test.
The starting figure is only an example.
Results
Volumetric flow
mm³/s
0.2 mm × 0.45 mm × 150 mm/s. That is 90% of a 15 mm³/s limit: close to the limit. The fastest speed that stays within the limit is 166.7 mm/s.
- Share of limit
- 90%
- Close to the limit
- Fastest within limit
- 166.7mm/s
- 15 ÷ (0.2 × 0.45)
- Filament feed
- 5.61mm/s
- 1.75 mm filament, 2.4053 mm²
How this was calculated
Flow, limit and feed speed with your numbers.
How this was calculated
Flow, limit and feed speed with your numbers.
Step 1: Volumetric flow
layer height × line width × speed
= 0.2 × 0.45 × 150
= 13.5 mm³/sEach millimetre of line is a small rectangle of plastic, layer height by line width. Multiply by how many millimetres the nozzle travels per second to get the plastic melted per second.
Step 2: Share of your limit
flow ÷ hotend limit × 100
= 13.5 ÷ 15 × 100
= 90% (close to the limit)The limit is the number you entered. Typical values are only a guide, so test your own hotend with your filament.
Step 3: Fastest speed within the limit
hotend limit ÷ (layer height × line width)
= 15 ÷ (0.2 × 0.45)
= 166.7 mm/sThis is the speed at which the flow just reaches the limit. Stay a little below it for a margin.
Step 4: Filament feed speed
flow ÷ (π × (diameter ÷ 2)²)
= 13.5 ÷ (π × (1.75 ÷ 2)²) = 13.5 ÷ 2.4053
= 5.61 mm/sThe filament is pushed into the hotend at this speed. At the limit it would be 6.24 mm/s.
In short
Flow = layer height × line width × speed. At 0.2 mm, 0.45 mm and 150 mm/s the flow is 13.5 mm³/s, which is 90% of a 15 mm³/s limit. The fastest speed within that limit is 166.7 mm/s.
You can type your own limit or pick a typical value.
Fastest speed by layer height
For a 0.45 mm line width and a 15 mm³/s hotend limit (an example, enter your own in the tool). Feed speed is for 1.75 mm filament at that top speed.
| Layer height | Plastic per mm of line | Fastest speed | Filament feed |
|---|---|---|---|
| 0.08 mm | 0.036 mm² | 416.7 mm/s | 6.24 mm/s |
| 0.12 mm | 0.054 mm² | 277.8 mm/s | 6.24 mm/s |
| 0.16 mm | 0.072 mm² | 208.3 mm/s | 6.24 mm/s |
| 0.2 mm | 0.09 mm² | 166.7 mm/s | 6.24 mm/s |
| 0.24 mm | 0.108 mm² | 138.9 mm/s | 6.24 mm/s |
| 0.28 mm | 0.126 mm² | 119 mm/s | 6.24 mm/s |
| 0.32 mm | 0.144 mm² | 104.2 mm/s | 6.24 mm/s |
These figures come from the formula. The real top speed also depends on acceleration and the shape of the print.
Typical hotend flow limits for PLA (ballpark)
Typical values only, not measurements or maker figures. Test your own hotend with a max-flow test and type the result into the tool.
| Hotend type | Typical limit | Top speed at 0.2 mm × 0.45 mm |
|---|---|---|
| Standard V6-style, 0.4 mm nozzle | about 12 mm³/s | 133.3 mm/s |
| High-flow style | about 20 mm³/s | 222.2 mm/s |
| Volcano-style | about 25 mm³/s | 277.8 mm/s |
| Very high-flow hotend | about 32 mm³/s | 355.6 mm/s |
Worked example: 0.2 mm layer, 0.45 mm line, 150 mm/s
With a 15 mm³/s hotend limit (an example) and 1.75 mm filament.
Step 1: Volumetric flow
layer height × line width × speed
= 0.2 × 0.45 × 150
= 13.5 mm³/sEach millimetre of line is a small rectangle of plastic, layer height by line width. Multiply by how many millimetres the nozzle travels per second to get the plastic melted per second.
Step 2: Share of your limit
flow ÷ hotend limit × 100
= 13.5 ÷ 15 × 100
= 90% (close to the limit)The limit is the number you entered. Typical values are only a guide, so test your own hotend with your filament.
Step 3: Fastest speed within the limit
hotend limit ÷ (layer height × line width)
= 15 ÷ (0.2 × 0.45)
= 166.7 mm/sThis is the speed at which the flow just reaches the limit. Stay a little below it for a margin.
Step 4: Filament feed speed
flow ÷ (π × (diameter ÷ 2)²)
= 13.5 ÷ (π × (1.75 ÷ 2)²) = 13.5 ÷ 2.4053
= 5.61 mm/sThe filament is pushed into the hotend at this speed. At the limit it would be 6.24 mm/s.
Before you raise your print speed
- The hotend limit is not a fixed number for a hotend. It changes with the filament, the temperature and the nozzle, so measure it and use your own value.
- Stay a little under the limit for a margin. The status shows "close to the limit" from 85% of it.
- If the printer slows down on its own in the slicer, set the maximum volumetric speed in the slicer to your measured limit so it does it for you.
- Speed also depends on acceleration, cooling and the shape of the part, so this number is a ceiling, not a target.
Volumetric flow: common questions
The formula, finding your limit and layer height.
What is volumetric flow rate in 3D printing?
It is the volume of plastic the hotend melts and pushes out each second, in cubic millimetres per second. It equals layer height × line width × print speed. A 0.2 mm layer with a 0.45 mm line at 150 mm/s needs 0.2 × 0.45 × 150 = 13.5 mm³/s.
How do I find my hotend's maximum flow?
Run a max-flow test: print a shape while the flow rises step by step (many slicers and calibration guides have one), and note where the extrusion turns thin, gappy or clicks. Take a value a little below that point. The result depends on your filament, temperature and nozzle, so the presets here are only a starting guess.
Why does the limit change with filament and temperature?
The hotend can only melt so much plastic as it passes through. Hotter filament melts faster, while some materials are stiffer or more viscous and flow less. A figure for PLA is not the figure for every filament, so test with the material and temperature you print.
How does layer height change the top speed?
A thicker layer needs more plastic per millimetre, so the speed that reaches your limit drops. With a 0.45 mm line and a 15 mm³/s limit, a 0.08 mm layer can go 416.7 mm/s, while a 0.32 mm layer tops out at 104.2 mm/s.