3D print time calculator: how long a print will take

The formula

A printer’s speed comes down to how much plastic it lays per second, averaged over the whole job. Divide the plastic by that rate and add the start-up.

plastic (mm³) = slicer grams / density x 1000, or the STL estimate
rate          = measured rate x layer height / measured layer height
                (never above the max volumetric speed)
flow time     = plastic / rate
layer floor   = layers x minimum layer time
print time    = the larger of flow time and layer floor
total         = print time + start-up

The plastic estimate is the STL cost calculator’s method. It wraps the surface in a shell of walls times line width and adds your infill share of the core.

The rate is an effective average, far below the hotend’s limit. Bambu Studio caps Bambu PLA Basic at 21 mm³/s, and PrusaSlicer caps generic PLA at 15 mm³/s. A whole job averages much less. The head brakes into every corner, outer walls and overhangs print slower, and travel moves extrude nothing. On a 3DBenchy the A1 mini averages 3.3 mm³/s, 16% of its cap.

The defaults are a 3DBenchy, read from the official STL (stereolithography) file: 15.55 cm³, 94.31 cm² of surface, 48 mm tall. It prints in PLA at 1.24 g/cm³ with 2 walls of 0.45 mm and 15% infill, as in Bambu Studio’s and PrusaSlicer’s 0.20 mm profiles. The minimum layer time is 6 s, Bambu Studio’s setting for Bambu PLA Basic on the A1 mini. Start-up is 4 minutes, what A1 mini owners report for heating and bed leveling.

Where the preset rates come from

Each preset is a 3DBenchy’s plastic divided by its print time.

Preset	Layer height	Benchy plastic	Benchy time	Rate
Bambu Lab A1 mini, 0.20 mm Standard	0.20 mm	9.55 cm³ (estimated)	48 min 3 s	3.3 mm³/s
Prusa MINI	0.15 mm	10.1 cm³	1 h 56 min 40 s	1.44 mm³/s
Prusa MK3S	0.15 mm	9.6 cm³	2 h 4 min 50 s	1.28 mm³/s

The Prusa rows come from the G-code files Prusa Research posts with the Benchy on Printables. Both the plastic and the time are PrusaSlicer’s own figures.

The A1 mini time is Igor’sLAB’s test print. Its plastic is this calculator’s estimate at the default settings, close to the 9.6 and 10.1 cm³ in Prusa’s slices. The review does not say whether its time includes start-up. If it does, the true rate is about 9% higher.

A Benchy is small and full of detail, so these rates sit at the slow end. Big, plain parts with long infill lines average more plastic per second. A rate measured on a model like yours beats any preset.

How do you calculate 3D print time?

Divide the plastic a print lays down by your printer’s average flow rate, then add start-up time. A 3DBenchy is about 9.55 cm³ of plastic. At 3.3 mm³/s that takes 48 minutes, plus about 4 minutes of heating and bed leveling. Find your own rate by dividing one sliced job’s volume by its time.

Worked example with the defaults

1. Shell: 94.31 cm² x 0.09 cm (2 walls x 0.45 mm) = 8.49 cm³.
2. Core: 15.55 - 8.49 = 7.06 cm³. Infill: 15% of that is 1.06 cm³.
3. Plastic: 8.49 + 1.06 = 9.55 cm³, or 11.8 g of PLA.
4. Rate: 3.3 mm³/s at 0.20 mm layers, under the 21 mm³/s cap.
5. Flow time: 9,547 mm³ / 3.3 mm³/s = 2,893 s, or 48 minutes.
6. Layer floor: 48 mm / 0.2 mm = 240 layers x 6 s = 24 minutes. That is shorter, so the plastic sets the pace.
7. Total: 48 + 4 = 52 minutes, shown as 0:52.

Measure your printer’s rate

1. Slice a model like the ones you print, with your usual profile and layer height.
2. Read the slicer’s filament grams and print time.
3. Enter both under “Measure your printer’s rate”. The rate fills in as grams / density x 1000 / seconds.

Prusa’s MK3S Benchy file, for example, holds 11.9 g of PLA and a 2 h 4 min 50 s estimate. That is 11.9 / 1.24 x 1000 / 7,490 s = 1.28 mm³/s. Once you have that rate, the calculator estimates new models from an STL before you slice them. For a model already sliced, the slicer’s own estimate is the better number.

Layer height and print time

At the same speeds in mm/s, plastic per second grows in step with layer height. The calculator scales your rate to match. The Benchy at 0.10 mm needs 1 h 36 min of printing instead of 48 minutes. Prusa’s knowledge base puts it plainly: taller layers significantly shorten the print, and thin ones cost time.

How long do 3D prints take?

A small print like the 3DBenchy takes from 14 minutes to about 2 hours, depending on printer and profile. It takes 48 minutes on a Bambu Lab A1 mini at 0.20 mm and 2 hours 5 minutes in Prusa’s 0.15 mm MK3S file. Larger prints take many hours, because time grows with the plastic.

Benchy times

Printer and profile	Layer height	Benchy time	Figure
Prusa MK4S, Prusa’s speed-tuned file	0.25 mm	14 min 11 s	PrusaSlicer estimate
Bambu Lab A1 mini, 0.20 mm Standard	0.20 mm	48 min 3 s	Igor’sLAB test print
Prusa MINI, Prusa’s file	0.15 mm	1 h 56 min 40 s	PrusaSlicer estimate
Prusa MK3S, Prusa’s file	0.15 mm	2 h 4 min 50 s	PrusaSlicer estimate

The MK4S file lays 8.35 cm³ in 14 min 11 s, 9.8 mm³/s. It runs 0.25 mm layers and 10% infill, tuned for speed rather than a default profile.

Average print time

There is no useful average, because print time follows the plastic. At the A1 mini’s Benchy rate of 3.3 mm³/s and 0.20 mm layers:

Plastic	Printing time
11.8 g (a Benchy)	48 min
50 g	3 h 24 min
200 g	13 h 35 min
1 kg	68 h

Large parts with long infill lines print faster than a Benchy, so treat these as the slow end. Your own measured rate gives your printer’s numbers.

Why is my 3D print taking so long?

Your printer lays down less plastic per second than its top speed suggests. Thin layers, extra walls, high infill, slow profiles and fine detail all cut the average flow. Small layers also wait out the slicer’s minimum layer time. Heating and bed leveling add minutes before the first line goes down.

What slows a print

• Thin layers. Printing at 0.10 mm instead of 0.20 mm doubles the flow time.
• Walls and infill. More plastic, more time. The default Benchy uses 11.8 g; printed solid it would be 19.3 g and take 63% longer.
• The profile’s speeds. Cura’s base profile prints at 60 mm/s with walls at 30 mm/s. PrusaSlicer’s 0.20mm SPEED profile for the MK4S runs perimeters at 170 mm/s and infill at 200. Bambu Studio’s 0.20mm Standard for the X1C runs outer walls at 200 mm/s, inner walls at 300 and infill at 270. A slow profile on a fast printer wastes the hardware.
• Detail and overhangs. Bambu Studio’s Standard profile prints small perimeters at half speed and the steepest overhangs at 10 mm/s. A Benchy is full of both, part of why it averages 16% of its cap.
• The volumetric cap. Raising speeds stops helping once the flow reaches the filament profile’s cap: 21 mm³/s for Bambu PLA Basic, 12 for Bambu Studio’s generic PLA, 15 for PrusaSlicer’s generic PLA.
• Minimum layer time. Each layer must take at least 4 s with Bambu PLA Basic on an X1C, 6 s on an A1 mini, 5 s in Cura and 6 s in PrusaSlicer’s MK4S PLA profile. A tall, thin part waits on every layer. Print several copies on one plate and they share that wait.
• Start-up. Owners report about 4 minutes of heating and leveling on an A1 mini. The calculator adds it on top of the printing time.

To turn the hours into money, the printer hourly rate calculator prices a machine-hour, and the electricity cost calculator prices the power.