3D Print Time Estimator
Which of the three terms actually decides your print time — and why a 2 mm move only reaches a quarter of the speed you set.
Speed actually achieved, by move length
The same part on each machine class
A 2 mm move reaches 26% of your set speed
Getting from rest to v at acceleration a takes v²/(2a) of distance, and you need it at both ends — so a move must be v²/a long to touch the set speed at all. At 150 mm/s and 3,000 mm/s² that's 7.5 mm. A 2 mm move averages 39 mm/s: twenty-six per cent of what the slider says. Below that threshold, raising the speed setting changes the time not at all — the move is over before the speed could ever have mattered.
So the setting that matters depends on the part, and people tune the wrong one. A large simple block is ~88% extrusion time, where flow rate is the whole lever and acceleration does nothing. A small detailed part is ~59% acceleration losses, where the speed slider is beside the point. A tall thin part hands a fifth of its time to per-layer overhead, which only a taller layer fixes. Three regimes, three different answers, one slider everybody reaches for.
It's also why high-acceleration machines feel faster than their headline speed suggests. At 10,000 mm/s² that same 2 mm move reaches 47% instead of 26 — nearly double the throughput on detailed geometry with no change to the speed number. Input shaping exists to permit that acceleration by cancelling the resonance it would otherwise excite, which is why it transforms detailed prints and barely registers on large simple ones.
- Per-layer overhead is invisible until the part is tall. A second a layer is three minutes across a 40 mm part and seventeen across a 200 mm one — and it's the only term a taller layer reduces directly.
- Slicer estimates are usually good and usually optimistic, for structural reasons rather than careless ones: they use the profile's acceleration rather than the firmware's real limits, they can't know about resonance compensation or pressure advance, and they assume no pauses. Treat one as a lower bound and calibrate the ratio once against a real print.
- Estimate the move length honestly. A flat face prints in long continuous passes; a lattice or a text emboss prints in very short ones with a travel between each. That's why detailed parts take far longer than their material use implies.
- Travel moves aren't counted here and aren't negligible on a part with many islands — they pay the same acceleration cost, and the retract-travel-prime cycle can rival the printing.
How to use
- Estimate the typical move length honestly — detailed parts print in very short ones.
- Read which of the three terms dominates before changing any setting.
- Raise acceleration for detailed parts and flow for large ones.
- Calibrate the ratio once against a real print and reuse it.
Frequently asked questions
Why is my 3D print slower than the speed I set?
Because the printer never reaches that speed on short moves. Getting from rest to the set speed takes distance, and you need it at both ends — at 150 mm/s and 3,000 mm/s2 a move has to be 7.5 mm long to touch the set speed at all. A 2 mm move averages 39 mm/s, which is twenty-six per cent of what the slider says.
Does raising print speed actually make prints faster?
On large simple parts, yes. On detailed ones, often not at all — below the ramp distance the move is over before the set speed could ever have been reached, so raising it changes the time by literally nothing. The setting that matters there is acceleration, and it is the one people almost never touch.
What is the ramp distance for my printer?
Set speed squared divided by acceleration. At 150 mm/s and 3,000 mm/s2 that is 7.5 mm; at 250 and 10,000 it is 6.25; at 100 and 1,000 it is 10. Any feature smaller than that number never sees the speed you configured, which is why small detailed parts feel disproportionately slow.
Why are high-acceleration printers faster than their speed suggests?
Because acceleration is what decides short moves and short moves are most of a detailed part. At 3,000 mm/s2 a 2 mm move reaches 26 per cent of a 150 mm/s setting; at 10,000 it reaches 47 — nearly double the throughput with no change to the speed number. That is also why input shaping matters: it exists to permit higher acceleration by cancelling the resonance it would excite.
What are the three components of print time?
Pushing plastic, which is volume divided by the achievable flow; per-layer overhead, which is the layer count times the fixed cost of a Z move and a prime; and acceleration losses, which is the time spent not at the set speed. Which one dominates changes completely with the part, and each has a different fix.
What makes a large simple part slow?
Flow, almost entirely — a large block runs about 88 per cent extrusion time. The moves are long enough to reach speed and there are few layers, so the only lever is how fast plastic can leave the hotend: a bigger nozzle, a taller layer, or a hotend that melts faster. Acceleration changes essentially nothing on a part like that.
What makes a small detailed part slow?
Acceleration, by a wide margin — a small detailed part can be 59 per cent acceleration losses. Every feature is shorter than the ramp distance, so the printer is permanently starting and stopping and never gets near its configured speed. Raising the speed setting achieves nothing; raising acceleration, or simplifying the geometry, achieves a great deal.
Why do tall thin parts take so long?
Per-layer overhead, which is invisible until the layer count is large. A second a layer is three minutes across a 40 mm part and seventeen minutes across a 200 mm one, and it is the only term a taller layer height reduces directly. On a very tall part it can exceed the time spent actually extruding.
Are slicer time estimates accurate?
Usually good and usually optimistic, for structural reasons rather than careless ones. Modern slicers do model acceleration, but they use the profile figure rather than the firmware actual limits, they cannot know about resonance compensation or pressure advance, and they assume no pauses. Treat an estimate as a lower bound and calibrate the ratio once against a real print — it is remarkably consistent per machine.
Does layer height change print time proportionally?
Not quite, because it acts on two terms at once and in different ways. It halves the layer count, which halves the overhead term outright, and it doubles the flow per pass, which helps the extrusion term only if the hotend can supply it. On a flow-limited machine a taller layer buys much less than the layer count suggests.
How do I estimate my typical move length?
Look at what the part actually is. A flat face or a large shell prints in long continuous passes of tens of millimetres; a lattice, a text emboss, a thin rib or anything with many small islands prints in passes of a few millimetres with a travel between each. If the part is a mixture, the small features dominate the time far more than their volume does.
Do travel moves count towards print time?
Very much so on a part with many separate islands, though this tool does not model them. They run faster than printing moves but pay the same acceleration cost, and each one usually comes with a retract and a prime. On geometry with hundreds of regions per layer that cycle can rival the printing itself, which is a reason to orient a part so it has fewer islands.
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