# Calculate the maximum flow rate of the extruder ### The melting rate

In order to calculate the maximum printing speed, we need to know how high the melting rate of the hotend is. Before we get started here, please make sure that you have calibrated your hotend using PID tuning, as fluctuating temperatures of the hotend directly affect the melting rate. ### Determine the maximum feed rate

First, heat up your hotend to the printing temperature, as soon as the temperature is constant begin to extrude filament with increasing extrusion's speed. We start by extruding 5 cm filament at 1 mm / s and then increase the extrusion speed until the extruder starts to lose steps. To do this, send the following command to your 3D printer: G1 E50 F60 (extrude 50 mm filament at 1 mm / s) Repeat this step and add 60 to the F (feed rate) setting. As soon as you notice that your extruder is losing steps, you take the last value before the extruder starts to lose steps. ### Calculation of the maximum flow rate

To calculate the maximum flow rate, we still need the diameter of your filament, measure your filament at various points and calculate the average filament diameter. Now we can use this formula.
Max flow rate = Max extrusion's speed * pi * (filament diameter / 2) ^ 2
Calculate the maximum flow rate. Let's assume that the max. Extrussion's speed is F600, then divide the 600 by 60 to get the speed / mm, this would be 10 / mm second here.
Max flow rate = 10 * pi * (1,715 / 2) ^ 2 = 10 * 3.14 * (1.75 / 2 * 1.75 / 2) = 24.05 mm³ / s

### Maximum flow rate calculator

Printer settings for the extrusion's multiplier:

Max. Extruder speed mm/s
Filament diameter: mm

New extrusion multiplier: 0 mm³/s