# Universal Dosage Calculator for Red Light Therapy! Find your optimal time per session!

How do you calculate the dose with your red light therapy device?

When you consume a pill, you are usually taking a certain amount of milliGrams (mG) over the course of a certain time frame. Usually you don't need to calculate anything like weighing out powders or breaking the pill in half - the dose is normally given to you in the proper weight and all you need to know is how many pills to pop at a time and how often.

The science of Red Light Therapy typically relies on the "dose" as the Energy delivered needing to be sufficient enough to deliver a particular biological response. Higher doses may mean the cells need more energy or to reach deeper tissues.

Energy is often measured in units of Joules (J). For large Red Light Therapy devices we prefer to dose in terms of Energy Density which is the Joules delivered per unit area. In the metric system, this becomes the Joules Per Centimeter Squared (J/cm^2).

However, the Power is the rate at which energy is delivered. The Power is in units of Watts. One Watt equals 1 Joule Per Second. Similarly we like to know the Power Density, often called the intensity or irradiance, which is Watts Per Centimeter Squared (W/cm^2).

Since we are typically using low intensities for proper Photobiomodulation, we shift the units from Watts to milliWatts. In the metric system the prefix tells you the order of magnitude. Where One Watt equals One Thousand MilliWatts. So we finally get the famous intensity units of mW/cm^2 (milliWatts Per Centimeter Squared).

Thereby we have the relationship between Time (seconds), Intensity (mW/cm^2), and Energy Dose (J/cm^2).

Dose (J/cm^2) = (Irradiance (mW/cm^2) * Time [seconds]) / 1000 [mW/W]

Often, we need to rearrange this algebra. Since we should know the intensity (irradiance) of our device, and know our desired dose from relevant clinical studies.

What we usually need to calculate is the Exposure Time to reach the desired dose.

Time [seconds] = (Dose [J/cm^2] x 1000 [mW/W]) / Irradiance (mW/cm^2)

Now, you can just "plug-in" the dose and intensity for your light into our handy calculator, and it will tell you how long to use it for!

The best part is that it works for ANY light-therapy light, as long as you have the accurate 3rd party irradiance measurements.

The "default" numbers above are actually for a GembaRed Rex at 0 inches with irradiance of 7mW/cm^2, and a desired dose of 6 J/cm^2. We see the time it takes to achieve that dose is 14.3 minutes.

Now the risk is that many companies may be false-advertising their intensity by over 2x with cheap solar power meters. When that happens, the outcome of using the calculator will be to use half has much exposure time. Thus, in reality you could be underdosing by 2x when you calculate the dose this way. So it is pertinent to insist on asking manufacturers for the most accurate intensity numbers they can provide ideally from professional 3rd party labs.

If a manufacturer can only provide Solar Power Meter measurements, you can use one of our 3rd party tested compensation factor calculators to get a more realistic intensity number for proper dosing. We have calculators for the Tenmars-TM206 and TES-1333 solar power meters.

#### 3/14/2024 - Quick Dosing Guide:

Studies on Full-Body Red Light Therapy are essentially non-contact systemic treatments. The typical range of effective doses is 20 to 33 J/cm^2 typically applied 3 times per week. Note the cumulative dose response, so daily doses would be reduced to 8 to 14 J/cm^2 if you want to do full-body red light therapy daily and avoid biphasic dose response of too frequent doses.

There is a biphasic response to having too much intensity and delivering doses in too short of time. Proper intensity for Photobiomodulation is typically between 5 to 50 mW/cm^2. Higher intensities may cause tissue heating, and PBM and LLLT are by-definition non-thermal light therapies.

Pulsed modes would need to use the Average Intensity in the calculator, not the Peak Intensity to get the proper Energy Density (J/cm^2). These parameters should be provided by the manufacturer, typically the Average Intensity is half of the Peak Intensity if we assume most devices will pulse with a 50% Duty Cycle.

Using high intensities (typically >50mW/cm^2) that cause heating are no longer a PBM Therapy but more of a Heat Therapy and will be dosed based on Skin Temperature and not Energy Density.

Direct Superficial doses (skincare, superficial wounds) typically range from 2 to 10 J/cm^2.

Direct deeper tissue doses range from 10 to 50 J/cm^2.

Read the dosing blog to learn about effective ranges of doses and the biphasic dose response. And how it is important to start with a reasonable dose and then titrate the dose up or down to find your personal optimal dose.

Reflection Compensation: Estimate about 60% of the light intensity will be reflected from the skin. So multiply your intensity by 0.4 or multiply the exposure time by 2.5 as a rough compensation.

Many studies use skin-contact method to eliminate reflection losses, optimize absorption, and enhance penetration by tissue compression and blanching the superficial blood from the skin.

A compensation factor for reflection losses may be required if you use a non-contact panel (i.e. >6 inches away) but referencing a study that is dosing with skin contact. This may be a crude compensation since it can only account for the loss of absorption and not the massive loss of penetration by tissue compression.

Bioindividuality: Additional dosing adjustments and considerations could be utilized based on Skin phototype (skin color) and gender

Total Joules: Some researchers prefer dosing based on the Total Joules, and not just J/cm^2. Read this blog to learn about Total Joules dosing.

#### Update 11/21/2023 - New Calculator! What Dose Are You Actually Getting?

The reverse of this math is to use Intensity and Exposure Time to quickly calculate what dose you are getting.

For example if a brand claims to emit >100mW/cm^2 at treatment distance, and they happen to recommend 10 minutes of exposure time.

You can now put those numbers into our calculator below to determine what is the dose that a manufacturer is recommending, or quickly find out the dose you have been actually getting.

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We can easily see with this calculator that intensities >100mW/cm^2 would quickly lead to overdosing. Which might be appropriate for some cases targeting deeper tissue, but typically we recommend starting with lower doses to see if you get better results.

#### Update 1/13/2022! Joules Per Centimeter Squared Per Minute?

In the never-ending efforts for companies to cover-up their false intensity claims, they may tell you to ignore intensity entirely and base your dosing calculations on the "J/cm^2 per minute."

The J/cm^2 per minute is a metric sometimes called "fluence" in the studies because it describes both energy and time together.

This is actually a nice convenience, because if you know you want a 10 J/cm^2 dose and a company tells you their fluence is 2.5 J/cm^2 per minute, then the math is a simple division and you know you need only 4 minutes to achieve that dose (minus reflection losses if you are standing 6 inches away).

But we know that the "J/cm^2 per minute" actually is easily converted to intensity of mW/cm^2 through the magic of simple math.

1 Joule/Second = 1 Watt

1000 mW = 1 W

1 minute = 60 seconds

So we know that when someone tells us the Joules/cm^2 per minute, that is a quick conversion equation.

mW/cm^2 = J/cm^2 per min * 1000 ÷ 60

For example:

2.5 * 1000 ÷ 60 = 41.66 mW/cm^2

That's it! Easy conversion from J/cm^2 per min back to mW/cm^2, the industry standard measurement.

#### Conclusions:

Remember that it is a common fallacy that "more power" means faster treatments. It has been shown that due to the biphasic dose response that the Law of Reciprocity does not always apply to light therapy. That a "faster dose" does not always mean the same effectiveness, although it might appear to save a busy person some time. Read more about intensity and effective doses on our earlier blog.

Ultimately there is still a lot left to learn about proper dosing with red light panels. But I feel we must be firmly grounded in the science and accurate measurements, otherwise we may never be able to replicate results or discuss photobiomodulation scientifically.

The science of Red Light Therapy still has a lot of grey areas in terms of how to properly dose the light! It is even more confusing by companies using inaccurate solar power meters, promoting high irradiances, and not always reporting the same units of intensity. And even the clinical studies report a wide range of dosages and intensities.