Dose Science
This page is the technical backbone of the dose calculator. The problem it is trying to solve is straightforward, but it causes a lot of confusion in practice.
Most studies do not prescribe "ten minutes of red light." They prescribe a dose. At home, most people copy a time.
Those are not the same thing.
Dose depends on how much light actually reaches your tissue, at your distance, with your device. Two people can both run a "10-minute session" and end up delivering very different amounts of energy. That alone explains a large share of the mixed results people report.
If you remember one line from this page, make it this: getting the dose wrong is the most common reason results look inconsistent.
In the research literature, protocols are usually defined by:
At home, devices differ in optics, beam spread, and real output at distance. So the same "session time" can mean very different biological exposures.
You can think of it like this:
The goal is not to turn you into an engineer. It is to stop "minutes" from being a guess.
Photobiomodulation is widely described as having a biphasic dose response. In plain terms:
This pattern shows up again and again in the PBM literature and is often discussed in the context of the Arndt-Schulz framework.
At the cellular level, red and near-infrared light interacts with mitochondrial pathways, especially cytochrome c oxidase, nitric oxide signaling, and downstream stress and repair processes. At sensible exposures, this can support energy metabolism and inflammatory regulation. Push the dose too far, and the same pathways can become counterproductive.
That is why dose matters more than enthusiasm.
In practical terms, many commonly cited ranges fall roughly around 5 to 50 J/cm2, depending on tissue and use case, with consumer setups often delivering something like 20 to 100 mW/cm2 at the target distance. The exact number matters less than staying in the right neighborhood and being consistent.
You do not need to obsess over every variable, but a few of them really do matter:
A sensible approach is boring, and that is a good thing: pick one goal, use a conservative protocol, keep your distance fixed, and adjust slowly.
Underdosing usually looks like "nothing happened." This is very common with low-output devices used too far away or for very short sessions.
Overdoing it can look like diminishing returns, irritation in sensitive users, or stalled progress despite putting in more time and effort.
This is why people can have completely opposite experiences with the same category of device. Often the disagreement is not about whether red light therapy can work in principle. It is about whether the delivered dose matches the biological window where it tends to help.
That is exactly the logic the calculator is built around.