Somewhere in the specs of most LED masks you will find a figure like "30 mW/cm²." Brands print it in bold. Almost none of them explain it, and the ones that do rarely mention the part that makes it hard to compare.
What it measures
Irradiance is how much light energy lands on a given area of skin at a given moment. Milliwatts per square centimetre. It is a measure of intensity, not of total treatment.
Total treatment is intensity multiplied by time. That figure is called fluence, or dose, and it is measured in joules per square centimetre. A lower intensity for longer and a higher intensity for a shorter time can deliver the same dose.
This is why intensity alone tells you less than it appears to.
Why the number moves
Here is the part that gets left out.
Irradiance falls off sharply with distance from the light source. Measure the same LED at one centimetre and at ten centimetres and you will get dramatically different readings from the same device.
So an irradiance figure is only meaningful alongside the distance it was measured at, and the method used. Almost no consumer brand publishes either.
Which means when you compare "65 mW/cm²" against "22 mW/cm²" from two different companies, you may not be comparing the same thing at all. You are comparing two unlabelled measurements taken under unknown conditions by parties with an interest in the result.
More is not automatically better
There is a common assumption that a bigger irradiance number is a better device. Researchers working in this field describe a biphasic dose response, meaning that below a certain dose there is too little effect, and above a certain dose the benefit does not keep climbing. The useful range is a range, not a ceiling to sprint towards. People make the same bigger-is-better assumption about price, which we look at in why LED masks cost $60 or $500.
A very high intensity figure also raises a practical question: at what distance, and for how long is the session? A high intensity paired with a short session may deliver a lower total dose than a moderate intensity over a longer one.
What to actually ask
Three questions cut through most of it:
- Is the number tied to a regulatory filing, or is it a marketing figure? A figure in an FDA clearance was submitted to a regulator. A figure on a landing page was written by a copywriter. If you are unsure what a clearance actually is, we wrote a plain explainer on what FDA cleared, registered and approved really mean.
- At what distance was it measured? If nobody will say, the number is not comparable to anything.
- What is the session length? Intensity without duration is half a sentence. We cover session length and frequency in how often should you use an LED face mask.
What BeamViva publishes, and where it comes from
These are our figures, and they are the ones in our FDA clearance, 510(k) K253086:
- 630nm red: 22 mW/cm²
- 605nm amber: 14 mW/cm²
- 460nm blue: 13.5 mW/cm²
- 850nm near-infrared: 3 mW/cm²
All ±20%. Session length is 15 to 25 minutes. The same figures are printed on the product page. If you are not sure what each of those four wavelengths is for, see which LED wavelength do you actually need.
We will be straightforward with you: on the headline red-light number, some masks quote higher figures than ours. What we can tell you is where our number came from and that you can verify it, which is not something you can do with a figure that only exists on a product page.
Ask the other brands the three questions above. See what you get back.