Protocol guide
Red light therapy dosing: the distance and time table nobody prints
Dose equals irradiance times seconds. Get the irradiance figure wrong and every session is wrong. Here is the arithmetic, the distance falloff, and why brand-published numbers usually overstate by about 2x.
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Red light therapy is the only category in home recovery where you can be doing everything right and getting a quarter of the dose you think, because of one number on a spec sheet.
Here is how to not do that.
The equation
Dose (J/cm²) = Irradiance (mW/cm²) × Time (seconds) ÷ 1000
Most published protocols target 10 to 60 J/cm² at the tissue. That range is wide because it varies by target — skin protocols tend lower, deeper musculoskeletal work tends higher.
Worked example: a panel genuinely delivering 70 mW/cm² at six inches, used for 10 minutes (600 seconds):
70 × 600 ÷ 1000 = 42 J/cm²
Comfortably inside the band. Now the same panel at twelve inches instead of six.
The distance problem
Irradiance falls off roughly with the square of distance. Double the distance, and you are receiving approximately a quarter of the energy.
| Distance | Approx. share of 6” irradiance | Time for ~42 J/cm² (from 70 mW/cm² @ 6”) |
|---|---|---|
| 6 in | 100% (70 mW/cm²) | 10 min |
| 9 in | ~44% (31 mW/cm²) | ~23 min |
| 12 in | ~25% (18 mW/cm²) | ~39 min |
| 18 in | ~11% (8 mW/cm²) | ~88 min |
This is why “I sit across the room from my panel while I work” is not a protocol. At eighteen inches you would need an hour and a half to reach a dose you get in ten minutes at six.
The practical consequence is not danger — it is that cross-brand comparison is meaningless unless you know the instrument. A panel advertising 200 mW/cm² measured on a solar meter may deliver less actual energy than one advertising 75 mW/cm² measured properly.
What to ask a brand
Three questions, in order:
- “Measured with what instrument?” Spectroradiometer or solar meter. If they will not say, assume solar meter.
- “At what distance?” Six inches is standard. A figure quoted at three inches is roughly four times a six-inch figure and is not comparable.
- “Centre or average across the panel?” Centre-of-panel is always the highest reading. Corners can be substantially lower.
Brands that publish both instrument readings — currently a very short list — are making themselves look worse on paper to be accurate. That is a reasonable proxy for whether the rest of their specs are honest.
Wavelengths and what they are for
| Wavelength | Commonly associated with | Penetration |
|---|---|---|
| 590 nm (amber) | Surface / cosmetic claims | Shallow |
| 630 nm | Skin | Shallow |
| 660 nm (red) | Skin, superficial tissue | Moderate |
| 810 nm (NIR) | Deeper tissue, joints | Deeper |
| 830 nm (NIR) | Deeper tissue | Deeper |
| 850 nm (NIR) | Deeper tissue, muscle | Deepest of the common set |
The three in bold carry most of the published evidence. Treat additional wavelengths as plausible extras rather than reasons to pay double — a well-built two-wavelength panel at 660/850 is not meaningfully compromised against a six-wavelength panel at the same measured irradiance.
A sane starting protocol
Not medical advice, and worth discussing with a clinician if you have any relevant condition:
- Distance: 6 inches for targeted work, 12 for larger areas with proportionally longer time
- Time: 10 minutes at 6 inches from a panel with genuine ~70 mW/cm²
- Frequency: 3–5 sessions a week rather than daily maximum exposure
- Eyes: do not stare into the panel; NIR is invisible and your blink reflex will not protect you
- Consistency: the reported benefits in the literature accrue over weeks and months, not sessions
Panel size does not change dose
A common and expensive misunderstanding: a bigger panel is faster, not stronger.
Two panels delivering identical irradiance deliver identical dose to any given square inch of skin. The 43-inch panel does not treat your knee harder than the 14-inch panel — it treats your knee, your thigh and your hip simultaneously, which means one session instead of three.
Buy size to match the body area you care about, and buy irradiance to control session length. Those are separate decisions and brands blur them deliberately.
FDA clearance, in context
Several red light devices carry FDA Class II clearances for specific indications such as temporary relief of minor muscle and joint pain. That is a regulatory clearance for a stated indication — it is not evidence for the broader claims that appear in marketing copy around energy, sleep, hormones or longevity.
Both things are true: the mechanism has real published literature behind it, and the marketing routinely outruns that literature by a wide margin.
Ready to buy? The best red light therapy panels of 2026, ranked on measured irradiance.
Questions buyers actually ask
How do you calculate red light therapy dose?
Dose in J/cm² = irradiance in mW/cm² × time in seconds ÷ 1000. Most published protocols target 10–60 J/cm². At a genuine 70 mW/cm², ten minutes gives 42 J/cm². The hard part is not the maths — it is getting a trustworthy irradiance number to put into it.
How far should I sit from a red light panel?
Six inches is the standard measurement distance and a sensible session distance for targeted work. Irradiance falls off roughly with the square of distance, so at twelve inches you receive about a quarter of the six-inch figure and need roughly four times the time for the same dose.
Can you overdose on red light therapy?
The literature describes a biphasic dose response — more is not linearly better, and very high doses may produce less benefit than moderate ones. Practically, this argues for staying inside commonly cited ranges rather than maximising exposure. It is not a burn risk at typical home-panel power levels, but longer is not automatically better.
How often should you use red light therapy?
Most protocols in circulation use three to five sessions a week rather than daily marathon sessions, on the reasoning that the response is biphasic and recovery time between exposures matters. Consistency over months appears to matter more than intensity in any single session.
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