I printed a lot of models in last month. I spent 2 kg filament in total. I want to know how many hours have been passed while printing. As far as I read, 1 kg PLA (1.75 mm) is about 110 meters long. My default print speed is 70 mm/s. The nozzle diameter is 0.4 mm. The nozzle multiplier in the simplify3d is 0.9 .

In a very basic math, 220÷(0.7×0.04÷0.0175×0.9)=~ 153 hours.

Is this correct?


2 Answers 2


Your formula doesn't seem to take into account two important factors: layer height and average speed.

Do the math differently:

voumetric flow rate [mm^3/s] = layer height [mm] * line width [mm] * speed [mm/s]

For example, 0.2 * 0.45 * 70 = 6.3 mm^3/s

which is realistic, the extruder on the Ender 3 cannot go much faster than that reliably.

PLA weighs 1.24 g/cm^3 = 0.00124 g/mm^3

To extrude 1 kg you need 1000/(0.00124 * 6.3) = 35 hours (70 for 2 kg).

However the printer does not reach 70 mm except on straight long moves, the average speed may be lower or much lower depending on what you print.

If you print technical parts with straight edges, maybe you can multiply by 1.5 (50 hours/kg), but if you print models and small statues or similar you may need to double it (70 hours/kg).

I use Klipper as firmware and I have a macro which keeps track of printing time and filament length used.

  • $\begingroup$ Yeah Klipper is very good but I didn't try yet. 1 Kg vs 70-90 hour made sense to me just as in my math. My models did not have very fine details, but they contained a lot of "support". I'm using ender 3 pro with 70 mm/s feed rate (and 100 mm/s xy speed). Layers are always set to 0.28. Extrusion multipler is 0.48 . With your math do it makes 85 hour? $\endgroup$
    – user30878
    May 27, 2021 at 19:49
  • $\begingroup$ @user30878 I don't use the extrusion multiplier, since that's a parameter used to calibrate the extruder. I use the final mass and volume of the print and the speed. What do you mean 70 mm/s feed rate and 100 mm/s xy? you canot feed 70 mm/s of filament. $\endgroup$
    – FarO
    May 28, 2021 at 14:05
  • $\begingroup$ in simplify3d, docs.aon3d.com/simplify3d/speeds_tab , I mean xy as the "xy axis movement speed" and "default printing speed" as the feed rate. $\endgroup$
    – user30878
    May 28, 2021 at 19:18

Your math looks correct, and is also a good approximation for what I've seen in the first few weeks with my own Ender 3.

Another way to calculate (to check yourself) is to calculate the volume extruded (nozzle area times extrusion percentage times print speed -- be sure you convert everything to the same units!) in a given second, multiply by the density of your filament (common PLA runs about 1.2 g/cm^3), and get a rough figure for how long it takes to print a kilogram of filament. Your actual print time will always be higher than this approximation, because there are moves during which the extruder isn't running, infill is often set to lower extrusion level, and of course there's setup and cleanup time to account for.

  • $\begingroup$ Yeah I know there will be extra time but at least this math shows the minimum passed time. Thanks for helping. I only needed the time the printer worked because I will calculate how much electricity I used. $\endgroup$
    – user30878
    May 27, 2021 at 12:43
  • $\begingroup$ Electricity calculations are tricky. Both the bed heater and the nozzle cartridge operate intermittently, with higher duty cycle at higher temperatures, lower when the room is warmer or if you have an enclosure -- and they're probably 90% of the power consumption of a printer like my Ender 3. If that's your main question, however, you should ask that as a question. There are ways to actually measure and record the consumption of a device over periods of time, too. $\endgroup$
    – Zeiss Ikon
    May 27, 2021 at 13:36
  • 1
    $\begingroup$ Yeah but I measured power consumption in various conditions before, I can make average estimations with those values. $\endgroup$
    – user30878
    May 27, 2021 at 17:06

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