Red Light Therapy
Dosage Calculator
Understand how irradiance and session time translate into light dose. Calculate surface energy density or find the time for a target dose.
Calculation examples
Illustrative inputs only. These are not product specifications or recommended treatment doses.
How to use this calculator
Find the right measurement
Confirm irradiance at the distance and light settings you will use. If your reading is already time-averaged, choose that value type.
Enter time or target dose
Calculate the energy density from a session length, or calculate time from a target supplied by your instructions or clinician.
Keep the context in mind
Distance, output uniformity, wavelength and device mode matter. Equal numerical doses do not guarantee equal biological effects.
Frequently asked questions
What does J/cm² mean?
Joules per square centimetre describes radiant energy delivered per unit surface area. With irradiance in mW/cm², multiply by time in seconds and divide by 1,000.
How do pulses affect the calculation?
For rectangular pulses with no light between pulses, multiply pulse-on irradiance by the duty fraction. If your meter or device specification already reports average irradiance in that mode, do not apply the fraction again. Frequency is not a dose multiplier.
Can I calculate from device wattage alone?
No. Electrical power does not tell you the optical irradiance at your skin. Use suitable measured irradiance or verified device data for your chosen distance.
Does this calculator tell me the best dose?
No. It is an educational conversion tool. It does not prescribe a dose, diagnose a condition or establish that a session is safe. Use your device instructions and seek clinical guidance when needed.
Why is total energy only an estimate?
Total energy equals dose multiplied by area when exposure is uniform. Real devices can have uneven illumination; use spatially averaged measurements for the area of interest. The result is not tissue-absorbed energy.
What should I check before a session?
Follow device directions on session length, distance and eye protection. Do not continue through discomfort. Ask a clinician before use if you have a photosensitivity condition, use photosensitizing medicines or are sensitive to flashing light.