Why is G-code feedrate in mm/min, not mm/s?

The F parameter in G-code (e.g. G1 X10 F3600) is defined in millimetres per minute by the RS-274 standard that CNC and 3D printer firmware follow. Slicers display speeds in mm/s for human readability, so a 60 mm/s setting becomes F3600 in the actual G-code.

What is the conversion formula?

Feedrate (mm/min) = speed (mm/s) x 60, and speed (mm/s) = feedrate (mm/min) / 60. So 50 mm/s equals F3000, and F4800 equals 80 mm/s. The factor of 60 is simply seconds per minute.

How is move duration calculated?

Duration = distance / speed. At a constant feedrate, a 30mm move at 60 mm/s takes 30 / 60 = 0.5 seconds. This ignores acceleration and jerk, so real moves are slightly slower on short segments, but it is accurate for steady-state long moves.

Does the F value persist across G-code lines?

Yes. Once set, the feedrate stays in effect for subsequent G0/G1 moves until a new F value is given. That is why slicers emit an F only when the speed changes, not on every line. Keep that in mind when reading raw G-code.

Does this apply to travel moves too?

Yes. Travel (non-printing) moves use the same F-in-mm/min convention, usually at a higher feedrate than printing moves. Convert travel speed the same way: 150 mm/s travel is F9000.

G-Code Speed & Feedrate Calculator

G-code expresses speed as a feedrate in millimetres per minute, but slicers and humans think in millimetres per second. This tool converts cleanly between the two and can also time a linear move, which is handy when reading or debugging raw G-code.

How it works

The conversion is a single factor of 60 (seconds per minute):

Feedrate (mm/min) = speed (mm/s) x 60

Speed (mm/s) = feedrate (mm/min) / 60

So a slicer print speed of 60 mm/s is written as F3600 in the G-code, and an F4800 you spot in a file is 80 mm/s.

Move duration uses distance over speed:

Duration (s) = distance (mm) / speed (mm/s)

This is exact for steady-state moves and ignores acceleration, so very short segments run slightly slower in reality.

Worked example

You set 80 mm/s outer walls in your slicer:

Feedrate = 80 x 60 = 4800 mm/min, written F4800
A 25mm wall segment takes 25 / 80 = 0.3125 s at that speed

Reading the reverse: a travel move tagged F9000 is 9000 / 60 = 150 mm/s.

Notes

The F value persists across lines until changed, so slicers emit it only when speed changes.
Travel moves use the same convention, usually at a higher feedrate than printing moves.
Use the duration figure to sanity-check segment timing; acceleration makes short moves slower than the ideal.

All conversions run locally in your browser.