Red Light Therapy Dose Calculator (J/cm²) for Hair and Skin
Your red light routine in 30 seconds
By your 16-week check you will have done 48 sessions.
Tip: the Folliq cap has a 10 or 20-minute timer and switches itself off.
The dose of a red light session, in J/cm², equals the irradiance at the skin in mW/cm² multiplied by the session time in seconds, divided by 1,000. Enter the numbers from any device’s spec sheet below to see its dose per session, per week and across 16 weeks, the period most hair studies measured.
For specialists: calculate the exact dose (mW/cm² → J/cm²) and compare devices
Try a published spec sheet:
Where your session sits
Markers show the published Folliq protocols. Use them to compare any device you are considering.
Your 16-week plan
Studies of red light devices measured results at 16 to 26 weeks. Here is your schedule with the settings above:
Compare two devices
Enter the spec-sheet numbers and price of two devices to compare dose and cost side by side.
Device A
- Dose per session
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- Dose per week
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- Cost per session (1 year)
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- Cost per month (1 year)
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Device B
- Dose per session
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- Dose per week
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- Cost per session (1 year)
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- Cost per month (1 year)
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The formula
Dose (J/cm²) = irradiance (mW/cm²) × time (s) ÷ 1,000
Example: 5 mW/cm² for 10 minutes (600 seconds) gives 5 × 600 ÷ 1,000 = 3 J/cm².
How to read the result
- Use the irradiance measured at the skin or scalp, in mW/cm². This is the number the dose formula needs.
- A short, bright session and a long, gentle session can deliver the same J/cm². Compare devices by dose per session and sessions per week.
- Photobiomodulation follows a biphasic dose response (Huang, Hamblin and colleagues, 2009): a moderate dose works best, so follow your device’s stated protocol.
- Hair studies of red light devices measured results at 16 to 26 weeks, which is why the calculator shows a 16-week total.
Folliq devices, in numbers
The Folliq Red Light Cap delivers about 5 mW/cm² (±20%) at the scalp from 650–660 nm red and 850 nm near-infrared LEDs: about 3 J/cm² in 10 minutes or 6 J/cm² in 20 minutes, 3 to 4 times a week. The Folliq Red Light Scalp Massager delivers 11.1 mW/cm² at 660 nm: about 4 J/cm² in its 6-minute session. For the full background on wavelength and dose, read our guide to low-level light therapy.
Frequently asked questions
How do you calculate red light therapy dose?
Multiply the irradiance in mW/cm² by the session time in seconds and divide by 1,000. The result is the dose (fluence) in J/cm².
How many J/cm² is one red light session?
It depends on the device. At 5 mW/cm², a 10-minute session gives 3 J/cm² and a 20-minute session gives 6 J/cm². At 11.1 mW/cm², 6 minutes gives about 4 J/cm².
Is a higher dose better?
A moderate dose works best. Photobiomodulation follows a biphasic dose response, so the reliable approach is your device’s stated session time and weekly schedule.
Can I convert watts to mW/cm²?
Use the irradiance at the skin, in mW/cm², from the manufacturer’s spec sheet. Total watts describe the whole device, while mW/cm² describes the light reaching each square centimetre of skin.
Cosmetic information tool. The calculator reports light dose from the numbers you enter; for medical questions, talk to your doctor. Results from studies vary from person to person.