Optical Watts vs Marketing Watts

The single most-confusing thing about diode lasers: the "watts" on the box almost never matches what comes out of the lens. Knowing the difference saves you from buying the wrong machine, or quoting the wrong job.

Three different "wattages" you'll see

• Marketing watts (input electrical): total electrical power consumed by the laser module. The biggest, most-prominently-displayed number. "40W diode!" usually means 40W of electricity going IN.
• Diode watts (chip output): output of the laser diode chip itself. Less common in marketing.
• Optical watts (out of the lens): actual usable laser power hitting your material. The number that matters. Usually 25-40% of marketing watts.

Real-world conversion

Marketing wattage	Typical optical output	Approximate equivalent CO2 power
"5W"	~1.5-2 W optical	Far weaker than any CO2
"10W"	~3-4 W optical	~5-10W CO2 cutting capacity
"20W"	~5-6 W optical	~10-15W CO2 capacity
"33W"	~10-11 W optical	~25W CO2 capacity
"40W"	~12-13 W optical	~30-35W CO2 capacity

These are approximate. Higher-tier brands (xTool, OneLaser) tend to deliver more optical W per marketing W than budget brands. ALWAYS check spec sheets for "optical output" specifically.

Why diode watts ≠ CO2 watts

Even at equivalent optical output, a diode and CO2 don't perform the same:

• Beam quality: diode beams have larger M² values (worse focus); spot size is bigger than CO2 RF metal-tube. So same optical W = lower power density at the workpiece.
• Wavelength: different absorption depending on material. Wood absorbs both well; clear acrylic absorbs neither well; diode handles painted/anodized surfaces in ways CO2 can't ablate as cleanly.
• Speed: diode max speeds are typically lower than CO2 due to gantry weight and stepper motor specs.

What this means for buying

• Don't compare diode watts to CO2 watts head-to-head. Look at MATERIAL CAPABILITY: "what's the thickest wood it cuts, what's the engrave time on a typical photo?"
• For paper / cardstock / leather: 5-10W marketing diode is fine.
• For wood cutting up to 6mm: 20W marketing diode minimum; 33-40W much better.
• For wood cutting 8mm+: 40W marketing minimum; honestly, switch to CO2 at this point.
• For high-detail engraving: beam quality matters more than wattage, premium diode (xTool S1, OneLaser) outperforms cheap 40W.

Spec terms to look for

When evaluating a diode, search the spec sheet for:

• "Optical power" or "laser output power", the truthful number.
• Wavelength: typically 445-455nm for blue diodes, 405nm for violet.
• Beam quality or spot size, smaller spot = finer detail.
• Diode chip count: "compressed spot" or "multi-diode" lasers stack multiple chips for higher optical output. xTool S1 uses 4-diode array.