How is laser speed and power communicated on this forum?

Hi all!

I just received my Glowforge late last week and have been cautiously experimenting with settings on non-proof-grade materials. I was hoping to get some suggestions to start from forum posts, but I’m a bit confused by the numbers getting tossed around.

I assume that [number]/[number] denote speed/power. However, speed numbers given here are way out of range vs what I see on the GFUI. For example, I see 60/60 or 40/50… but speeds on GFUI range from 100 to 1000.

I assume the scale got changed somewhere in the middle of beta, but I can’t find a comprehensive explanation of this transition. Could someone explain or point to the right resources?

Thanks! And sorry if this had been asked before.

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Yes, they used to use real units, but for reasons only understandable by @Dan, they chose to switch motion to an imaginary unit which goes to 1000 (is that like Spinal Tap’s it goes to 11?). In the original PRU period we all happily used normal speed (measurements distance/time). Eventually this will either drive you bananas or you just accept it as the absurd way it is (yes, this means you can’t easily convert from other 40w laser’s suggested settings…


Speed used to be in inches per minute and were odd values because the machine itself uses mm / minute. Now it is in an arbitrary scale that has both a scale factor and an offset, so doubling the speed figure is not twice as fast. Also the units are slightly different when engraving versus cutting.

Here are the formulas to convert to and from real world units.

cut = 100 + 400 * (ipm - 4) / 153

engrave = 100 + 900 * (ipm - 4) / 331

ipm = 4 + (cut - 100) * 153 / 400

ipm = 4 + (engrave - 100) * 331 / 900


All the above plus we have gone to calling power and speed pews and zooms. So if you get something nailed down and want to share just give pew and zoom and put it in beyond the manual.


Ditto what @henryhbk said.

Here’s the spreadsheet GF released (download a copy) when the came out with what they called “Precision Power” this summer.


Just to confirm, the formulae posted by @palmercr above, and the spreadsheet only address speed, right? Power units stay unchanged?

No they changed the power scale as well but that was never in sensible units.

All we are told is full is 40W on the basic and 45W on the pro. 100 is a lower power that is the same on both machines. The scale 1-100 appears to be linear.


They really need to put the converter as a page in the app, or better yet add advanced mode with unit conversions.


Sort of. The 1-100 scale is the same and could be resulting in the same power delivered. Or not, no way to tell. It could be % of 40W or it could be an arbitrary 1 to 10 scale like on your stereo. Some folks belief that since it’s not in Watts it’s meaningless - although I’m not sure what 7 watts means other than, umm, 7. It’s only meaningful relative to other watt settings. Nor is a % likely to do any more good - lots of folks use % and unless you know what the base is that’s meaningless too - might give a sense of precision but it’s illusory. Does 50% of a 60W Redsail = 30W or 35W or 25W? Some tube ratings are nominal (my K40 “40W” tube is actually only 32W - it hits 40W only when over powered). So is the % you see from other machines the % of the true power or of the rated power or of the over powered power?

But the GF idea is that power settings between 1-100 will deliver the same results on either the 40W Basic or the 45W Pro. According to Dan the only difference is in the power delivered at “Full” where the Pro’s Full is more power than the Basic’s Full.

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Thanks for sharing the formulas.


Thanks for the answer @palmercr, that’s right. I’m going to close this thread - if you still have questions, go ahead and post a new topic or reach out to Thanks for reaching out!