Optical Watt Calculator
The wattage on the box is almost never the wattage doing the work. It is usually measured at the plug or at the module input, before conversion losses and before the beam has been through a lens, a window and however many mirrors. What cuts is the optical power arriving at the focus. Put the advertised figure in, say which end of the machine it was measured at, and get the delivered number — plus the energy density that actually decides whether a pass goes through.
A 445–455 nm multi-emitter module turns roughly a third of the electrical power it is fed into light. One focusing lens plus its protective window passes about 92% of that to the workpiece.
The advertised number describesMost machines sold as a 20 W or a 40 W are quoting draw at the plug or into the module. Only pick Stated optical when the seller has printed an optical figure and named where it was measured.
Electrical in, light out.
Mirrors, lens, window.
What that power does at the focus
Delivered watts on their own decide nothing. Concentrated into a small spot they cut; spread across a fat one they scorch. Add your spot size and feed rate for the two figures that actually predict a cut.
Diode spots are rectangular — use both figures.
Optional — the speed of one pass.
Once you know the real optical output, work out how far it stays dangerous with the NOHD and eye-safety calculator.