Step 6 of 9
Flow Rate /
Extrusion Multiplier (EM)
Find the perfect amount of plastic for accurate dimensions, strong parts and clean surfaces.
⏱
Time
15–25 min
📊
Difficulty
Intermediate
⚡
Impact
High
Why this matters: Flow Rate (EM) controls how much plastic is actually deposited.
Too high (over extrusion):
• Elephant skin, rough surfaces
• Bulging corners
• Dimensional inaccuracy
Too low (under extrusion):
• Gaps between lines
• Weak walls
• Poor top layers
OVER EXTRUSION
EM = 1.08
Bulging corners,
thick walls,
elephant skin
thick walls,
elephant skin
CORRECT FLOW
EM = 0.98
Clean surfaces,
accurate dimensions
accurate dimensions
UNDER EXTRUSION
EM = 0.90
Gaps between lines,
weak walls,
top surface issues
weak walls,
top surface issues
⭐ Recommended Method
💡
Pro Tip — Skip Pass 1
If your extruder is properly calibrated and your filament diameter is correct, flow rate almost always lands between 0.96 – 1.00. Set flow to 1.000 in your filament profile and go straight to Pass 2 — you'll find your value in the first few blocks. 😉
1
How to Print⚙️
Set flow to 1.000
In your filament profile, set Flow Ratio / EM to exactly 1.000 before starting.
🖨️
Run Pass 2 in slicer
OrcaSlicer / Bambu Studio → Calibration → Flow Rate → Pass 2. Slice and print.
🔍
Inspect the 10 blocks
Blocks are labeled 0 to -9. Find the one with the cleanest surface — no gaps, no elephant skin.
💻
Enter block number
Tell us which block won. We calculate your EM — no calipers needed.
2
Pick Your Best BlockWhich block had the cleanest top surface and sharpest edges? No calipers — just your eyes.
Block number
Each block modifier is shown below the number. Block 0 = no change, block -9 = −9% flow.
3
Your EM🎯
Select your best block on the left to see your EM.
Formula
EM = current × (1 + block × 0.01)
🔧 Legacy Method
This was the standard method before slicers had built-in flow calibration. Use it to verify or fine-tune after Method 1, or if you don't use OrcaSlicer / Bambu Studio.
1
How to Measure🖨️
Print the test piece
Use a single-wall calibration cube or provided test model. 1 perimeter, no infill.
📐
Measure the walls
Use calipers to measure the wall thickness on multiple sides — at least 4 measurements.
🔢
Calculate the average
Average all measurements for the most accurate result. Don't just use one side.
💻
Use in calculator
Enter the values to get your recommended Flow Rate (EM).
⭐ Pro Tip
Measure at least 4 sides and average them for the most reliable result. Let the part cool completely before measuring.
2
Enter Your MeasurementsStart with 1.000 if not previously calibrated.
mm
Usually = nozzle diameter (0.4mm nozzle → 0.42mm typical)
mm
Make sure to measure the printed part after it has completely cooled down.
3
Your Result📊
Enter your measurements and click Calculate to see your recommended EM.
Formula
new_EM = current_EM
× expected / measured
× expected / measured
⊗Common Mistakes
⊗Calibrating before Pressure Advance
⊗Using top surface only for measurement
⊗Using a wet filament
⊗Changing temperature afterwards
⊗Applying the same EM to all filaments
⭐Pro Tip
Most calibrated filaments end up below 1.00. Typical range:
0.92 – 1.00
Every filament is different. Calibrate for each one you use.
→Next Step
Retraction
Eliminate stringing by dialing in the perfect retraction settings.
Go to Retraction →✉️CN3D Insider
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