Browser-only OrcaSlicer calibration tool
Flow Ratio Calculator
Pick the flow ratio method you are actually running, enter the two numbers it gives you, and the page returns the corrected flow ratio to save in your filament profile. OrcaSlicer’s own Flow Ratio test uses additive modifiers or percentage modifiers read from a printed top surface; the wall-thickness estimate is a different procedure and is labelled as one here. Everything is plain arithmetic in this page — nothing is uploaded, stored or printed for you.
Result
Choose a method, enter the current flow ratio and the number your test gave you, then select Calculate flow ratio. No result is shown until every value the selected method needs is valid.
Corrected flow ratio —
Displayed rounded to at most 6 decimal places. The page does not round, clamp or store the value for you.
Record
Copy this into your own notes. The preset and outcome lines are left blank on purpose: this page cannot print, measure or verify anything, so it does not fill them in.
Which formula the page applies
OrcaSlicer documents two modifier-based Flow Ratio calibration methods, and the wall-thickness method below is a third, older procedure. They are not interchangeable, so the page names the method it used next to every result.
YOLO additive modifier (single pass)
new flow ratio = current flow ratio + selected modifier
The published example: a profile at 0.98 whose best block carried a +0.01 modifier becomes0.98 + 0.01 = 0.99.
Legacy percentage modifier (two passes)
new flow ratio = current flow ratio × (100 + selected percentage modifier) ÷ 100
The published examples: pass 1 from 0.98 with+5 gives 0.98 × (100 + 5) ÷ 100 = 1.029, and pass 2 starts from that corrected value, not from 0.98 —1.029 × (100 − 6) ÷ 100 = 0.96726.
The two units are not the same thing. A+0.01 additive modifier moves 0.98 to 0.99, which is about +1%. It is not a +5% percentage modifier, and it is not “+1 percent” applied to the ratio either. Use the number printed on the test you actually printed.
Measured-wall estimate (separate method)
new flow ratio = current flow ratio × (target wall ÷ measured wall)
A profile at 1.000 sliced a cube with a0.40 mm line width and the printed wall measures0.44 mm, so1.000 × (0.40 ÷ 0.44) = 0.909. This is arithmetic on a caliper reading: it is not OrcaSlicer’s built-in test, it has no passes, and no amount of calculation replaces a reprint.
Running the tests in order
- Slice and print the flow ratio test your OrcaSlicer build offers, then read the result from the printed top surface: the block that looks best tells you which signed modifier to use.
- Read the current flow ratio from the filament profile and select the matching method here.
- Enter the modifier (or the caliper readings, for the wall estimate) and calculate.
- Save the corrected value in Filament settings → Filament → Flow ratio. Neither this page nor the test does that for you.
- Legacy method only: run the second pass as a fresh calculation, with the value you just saved as the current flow ratio.
- Reprint and inspect before trusting the profile on a real model.
What a corrected flow ratio can and cannot fix
- It changes extrusion volume. Flow ratio is the extrusion multiplier: it scales how much filament the slicer asks for, which is what an under- or over-extruding test patch is responding to.
- It is spool-, nozzle- and printer-specific. The value belongs to the filament profile you calibrated on that machine. A different spool, nozzle or extruder needs its own calibration.
- It does not fix mechanical problems. A partial clog, loose belts, a worn nozzle or a slipping extruder will corrupt the print you are reading. Fix those first.
- It guarantees nothing. This page does arithmetic on the numbers you type. It does not print a test, measure one, or prove dimensional accuracy or correct extrusion — only a print you inspect can do that.
- Reading the test is the hard part. Surface differences between neighbouring blocks are subtle, and caliper readings move with wall bulge, seam placement and jaw pressure. Average several points and compare two adjacent candidates before deciding.
Frequently asked questions
Which method should I use?
Use the method that matches the test you printed. If your project documentation lists the YOLO additive modifiers, that single-pass method is the current one; the legacy percentage method is the two-pass workflow older builds and guides describe. The measured-wall estimate is a separate caliper procedure for when you have no modifier test to read.
Where do I find the current flow ratio in OrcaSlicer?
In Filament settings, on the Filament tab, in the Flow ratio field. Every filament profile stores its own value, so check the profile you are calibrating rather than the printer settings.
Is a +0.01 modifier the same as +5%?
No. The additive modifier is added: 0.98 + 0.01 = 0.99. The percentage modifier scales the ratio: 0.98 × (100 + 5) ÷ 100 = 1.029. They are different units from different tests, and mixing them up moves the value much further than intended.
How does the second pass work?
Pass 2 repeats the same calculation with the corrected value from pass 1 as its original flow ratio. The legacy test’s second project prints modifiers from −9 to 0, and you apply the one from the block that looks best. If that result sends you back past the block you liked in pass 1, reprint and look again instead of stacking another modifier on top.
Is flow ratio the same as extrusion multiplier?
Yes. OrcaSlicer labels the field “Flow ratio”; older slicing guides call the same number the extrusion multiplier. Enter whichever value your profile shows.
Does the calculator send my values anywhere?
No. The calculation is plain arithmetic that runs in this page, and no value you type is stored, logged or transmitted. Copying a record writes to your own clipboard.
Sources
- OrcaSlicer wiki — Flow ratio calibration
The project’s own description of the YOLO single-pass method, the legacy two-pass percentage method, and the modifiers each test prints.
- OrcaSlicer source repository
Slicer code, releases and issue tracker, for anything the wiki does not answer.
Put the value to work
The corrected flow ratio belongs to the preset you actually tested: that spool, that nozzle and that printer. Save it there, and confirm it again whenever any of those conditions change.