What Is Irradiance in Red Light Therapy?
What is irradiance in red light therapy?
Quick answer: Irradiance is the amount of light power reaching each square centimeter of a surface, measured in milliwatts per square centimeter (mW/cm²). It is a key specification to check on any red light device, because the same panel delivers very different amounts of light depending on how far away you sit.
Why it matters
Two panels with identical wavelengths and LED counts can deliver very different amounts of light if their irradiance numbers differ. A number measured at the LED surface says little about the number at a typical sitting distance. As an example (numbers for arithmetic only), a panel listed at 200 mW/cm² at the surface might read 30 mW/cm² at 6 inches. Without an irradiance chart that shows several distances, you cannot know how much light reaches you.
What to ask before buying
- What is the irradiance at several distances, such as 6, 12 and 18 inches? The number changes with distance.
- How was it measured? Independent third party measurement with a calibrated meter is the best source.
- Is the measurement at the center or averaged across the panel? Center only readings can overstate the number.
AWA FX500 published irradiance
The AWA FX500 publishes 220 mW/cm² at 2 inches, 149 mW/cm² at 4 inches, 94 mW/cm² at 6 inches and 73.8 mW/cm² at 12 inches. To turn irradiance into energy per session, use the formula J/cm² = mW/cm² × seconds ÷ 1000. The full table is in our FX300 and FX500 irradiance specs guide.