Print time is the input that decides machine cost, electricity cost and whether a job is worth quoting. This estimator gives a figure from part volume, layer height, nozzle diameter and print speed, and this page explains where it comes from and where it goes wrong.
The model
Extrusion is a volumetric process. The plastic laid down per second is layer height multiplied by extrusion width multiplied by print speed, which gives a volumetric flow rate in cubic millimetres per second. Divide the part's volume by that rate and you have a first estimate of print time.
At a 0.2 mm layer, a 0.45 mm extrusion width and 150 mm/s, that is 13.5 mm³/s. A 100 cm³ part is 100,000 mm³, so the ideal time is about 7,400 seconds, or a little over two hours.
Reality is longer, always. Travel moves lay down nothing. Perimeters print slower than infill. Small layers finish faster than the machine can accelerate through them. And the extruder cannot always supply the flow the speed setting implies.
The two limits that decide the real answer
Acceleration. On short segments the toolhead never reaches its commanded speed. A model full of small detail spends most of its time accelerating and decelerating, and raising the speed setting changes almost nothing. This is why a detailed miniature and a plain cube of the same volume can differ by a factor of three in print time.
Volumetric flow. Every hotend has a ceiling on how much plastic it can melt per second — often 8 to 25 mm³/s on a mainstream hotend, higher on a high-flow one. Ask for more than that and the printer either slows down on its own or under-extrudes. A speed setting above the flow ceiling is a number that does not describe what the machine will do.
Why nozzle size beats print speed
Because flow is the product of three terms and the nozzle raises two of them at once. Moving from a 0.4 mm nozzle to a 0.6 mm increases the extrusion width by half and allows a taller layer, and because those multiply, a solid part can print in roughly half the time at the same head speed.
Raising speed alone eventually hits the flow ceiling and stops helping. Raising nozzle diameter raises the ceiling itself. If a print is too slow, the nozzle is usually the more effective lever, and the detail you give up is often irrelevant on a functional part.
Why this will not match your slicer
Your slicer has the actual toolpath. It knows every travel move, every acceleration segment, every seam and every retraction, and it still tends to be optimistic because its motion model does not fully capture your machine's real limits.
This estimator has only the summary figures, so treat it as a planning number rather than a schedule — good for deciding whether a job is a two-hour or a twenty-hour proposition, not for promising a collection time.
Making it accurate for your machine
Time one real print and compare it with the estimate. The ratio is your own correction factor, and applying it to future estimates will get you far closer than any generic model. Track it separately for detailed and for chunky parts, because the acceleration effect makes those two categories behave very differently.
Once you have a reliable time figure, the cost calculator can turn it into an electricity and machine-time cost.
What to do with the number
Two things. First, decide whether the job is worth running at all — a part that takes thirty hours on a machine you need tomorrow is a different decision from one that takes three, regardless of what it costs.
Second, feed it into cost. Print time multiplies both the electricity term and the machine-time term, so it is the input with the widest reach in any cost estimate. A 20% error in time is a 20% error in two of the four cost terms.
The setting that costs time without buying anything
Layer height on non-visible surfaces. Halving layer height roughly doubles print time and does nothing measurable for a functional part's strength — thinner layers mean more welds, not better ones. If nobody is going to look at the surface, print it coarse.