660nm vs 850nm Red Light Therapy: Wavelength Differences Explained
Published May 25, 2026. Updated October 2026.
Quick answer
660nm is visible deep red and 850nm is near infrared, mostly invisible to the eye. AWA panels pair 30 LEDs at 660nm with 30 at 850nm. Read a spec sheet for the exact wavelengths, whether irradiance is per wavelength or combined, and the distance. This guide describes light and does not claim any wavelength does anything for a person.
What the numbers on a spec sheet mean
When you shop for a light device you will see numbers like 660nm and 850nm. The letters "nm" stand for nanometers, a unit of length, and the number is the wavelength of the light. Wavelength is what sets the color of visible light, and light past the red end of the visible range is called near infrared. This guide is a plain language explanation of the wavelengths you will meet and how to read them on a spec sheet. It does not claim that any wavelength does anything for a person, because we make no claims about outcomes.
Wavelength table
| Wavelength | Color | Typical device feature | What to check |
|---|---|---|---|
| 415 nm | Blue (visible) | A blue mode on multi color masks; the AWA LX300 page lists 415nm | That the manual gives eye directions for the blue mode |
| 630 nm | Red (visible) | A red mode on masks; the LX300 page lists 630nm | Whether the sheet states the wavelength or just says red |
| 660 nm | Deeper red (visible) | One half of the paired 660nm and 850nm LEDs on the AWA FX300 and FX500 panels | LED split, irradiance at a stated distance |
| 810 nm | Near infrared (mostly invisible) | Found on some devices as an alternative to 850nm | Whether it is listed on the sheet at all |
| 850 nm | Near infrared (mostly invisible) | The other half of the FX panel pairing; also a mode on the LX300 | Whether you can tell it is on, and the timer or indicator the device uses |
Colors and positions are described in general terms. Only wavelengths listed on an AWA product page are tied to an AWA device.
The table has four columns because those are the four questions to ask about every wavelength a device lists: what it is, what it looks like, where it tends to appear, and what to verify.
660nm and 850nm on AWA panels
The AWA FX300 and AWA FX500 panels pair 660nm and 850nm LEDs. Our irradiance specs guide describes 60 LEDs of 5W each, 30 at 660nm and 30 at 850nm, and the FX500 page describes the pairing as a 1:1 ratio. That tells you how the emitters are divided, not how the light divides between wavelengths on your skin, because LEDs at different wavelengths can have different output.
The LX300 mask page lists red at 630nm, near infrared at 850nm and blue at 415nm, plus additional color modes. The LX500 page lists red, yellow, blue and near infrared modes. If you want the wavelength behind each mode, check the manual.
Visible versus invisible
660nm is visible as a deep red. 850nm is near infrared and is mostly invisible to the eye. This has a practical consequence unrelated to any claim about outcomes: you cannot judge by looking whether the 850nm LEDs are on, how bright they are, or whether a panel is working as designed. Rely on the device's indicator, timer and manual, and use eye protection as directed, since brightness is not a reliable cue for near infrared.
Arithmetic: the same power does not mean the same number of photons
Light is delivered in packets called photons, and each photon carries energy that depends on wavelength: energy in eV = 1239.84 / wavelength in nm. A 660nm photon carries about 1.88 eV and an 850nm photon about 1.46 eV, so the same milliwatts at 850nm means more photons per second than at 660nm.
| Wavelength (nm) | Photon energy in eV (1239.84 / nm) | Photons per second at equal power, relative to 660 nm |
|---|---|---|
| 415 | 2.99 | 0.63 |
| 630 | 1.97 | 0.95 |
| 660 | 1.88 | 1.00 |
| 850 | 1.46 | 1.29 |
Physics arithmetic only. It says nothing about what any wavelength does for a person.
Arithmetic example: 850 / 660 = 1.29, so at equal power an 850nm source emits about 1.29 times as many photons per second as a 660nm source. This is a statement about physics. It is not a statement that more photons are better or that either wavelength does anything in particular.
Arithmetic: per wavelength versus combined figures
Some spec sheets give one irradiance number for a whole device, others give a number per wavelength. The two are not interchangeable.
Arithmetic example with invented numbers: a hypothetical sheet lists 40 mW/cm² at 660nm and 40 mW/cm² at 850nm. For 10 minutes (600 seconds), each wavelength delivers 40 x 600 / 1000 = 24 J/cm². The two together total 48 J/cm². If another hypothetical device lists a single combined figure of 80 mW/cm², the same 10 minutes gives 80 x 600 / 1000 = 48 J/cm² in total, but you cannot tell how it splits. Comparing 40 with 80 without noticing which is per wavelength and which is combined would be a mistake. The energy formula itself is in our dose calculation guide.
Choosing between devices by wavelength list
- Write down which wavelengths each device lists, and whether they are stated as exact numbers or as color names.
- Check whether irradiance is given per wavelength or combined, and at what distance.
- Note whether the device is a panel, a mask or a wearable, because the working distance differs.
- Read the manual for eye directions on each mode, especially blue and near infrared.
- Read the product page and label. Select devices carry FDA 510(k) clearance for specific, limited uses, and most light devices are sold as general wellness products.
Common mistakes
- Comparing "red" on one sheet with "660nm" on another as if they were the same statement.
- Reading a per wavelength irradiance figure as if it were a combined figure, or the reverse.
- Assuming a device is not emitting because you cannot see 850nm light.
- Counting LEDs per wavelength as if it were output per wavelength.
- Reading wavelength lists as claims about outcomes. They describe the light, nothing more.
- Using the blue mode of a multi color mask without reading its eye directions.
Before you use any light device: read the label, follow the device manual, and use eye protection as directed. Ask a doctor first if you have a medical condition, take medications, are pregnant, or have light sensitivity.
Related guides in this series
- What irradiance means on a spec sheet
- AWA FX300 and FX500 irradiance specs
- Eye protection and goggles guide
- How to calculate a red light therapy dose
- Red light therapy myths guide
Device pages
Read the full page and label for each device before you use it: AWA FX300 panel, AWA FX500 panel, AWA LX300 face mask. You can also browse all AWA red light therapy devices.
Frequently asked questions
What does 660nm mean?
It is a wavelength of 660 nanometers, which is a deep red color of visible light. It is a spec sheet number that describes the light a device emits.
What does 850nm mean?
It is a wavelength of 850 nanometers, in the near infrared range. It is mostly invisible to the eye, so you cannot judge by looking whether it is on.
Which wavelengths do AWA panels list?
The AWA FX300 and FX500 pages list 660nm and 850nm. The irradiance specs guide describes 60 LEDs, 30 at 660nm and 30 at 850nm.
Are the wavelength figures on spec sheets exact?
Sheets may state a nominal wavelength, and real LEDs can vary slightly around it. A clear sheet states the wavelength and says whether a tolerance applies.
Do I need eye protection with near infrared?
Use eye protection as directed in your device manual. Because 850nm is mostly invisible, how bright the light looks is not a reliable guide.
Sources
- FDA: General Wellness policy guidance (CDRH). Final guidance dated January 2026 that sets out the agency's compliance policy for general wellness products. It is a policy document, not a statement about any one device.
- FDA: Laser Products and Instruments. Describes FDA laser hazard classes I to IV, notes that higher classes carry warning labels, and states that LEDs are not subject to the federal laser product performance standard.
- FDA: Premarket Notification 510(k). Explains that a 510(k) is a premarket submission showing a device is substantially equivalent to a legally marketed device, and that a company must receive an FDA order clearing the device before marketing it in the U.S.
Regulatory note: select devices carry FDA 510(k) clearance for specific, limited uses. Most light devices are sold as general wellness products. Read each product page and label.
How we create this guide
AWA sells red light therapy devices. We write these guides to explain how devices work and how to choose and use one. This is general information, not medical advice. Read each product page and label. See our editorial standards.
