Red Light Therapy Timer
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Common uses for a red light therapy timer
- Timing panel sessions
- Converting a target dose into minutes
- Consistent session structure
- Tracking exposure across a routine
Red light therapy session length is not a fixed number — it follows from the device. The delivered energy is irradiance multiplied by time: a device producing 100 mW/cm² delivers 6 J/cm² in a minute, while one producing 20 mW/cm² needs five minutes for the same. Any session length quoted without an irradiance figure is meaningless.
Ten minutes is a common session length for consumer panels, which typically produce lower irradiance at the distances people actually use them. The number that matters is the total energy delivered, and the only reliable way to know it is the device's own specification at your working distance.
The arithmetic
Energy density in J/cm² equals irradiance in mW/cm² multiplied by time in seconds, divided by 1000. So 50 mW/cm² for 120 seconds gives 6 J/cm². That is the whole calculation, and it is the reason two devices need very different session lengths.
Irradiance falls off sharply with distance. A panel specified at 100 mW/cm² at 15 cm may deliver a fraction of that at 45 cm, so a session length copied from someone else's routine at a different distance does not transfer.
Follow the device instructions
Manufacturers specify session lengths and distances for their own hardware, and those instructions are the authority for that device — not a general figure from an article, including this one.
Manufacturer irradiance claims are also not uniformly reliable, which is a known problem in the consumer market. Where a third-party measurement exists for your device, it is worth more than the specification sheet.
What this page does not do
This page explains how session length relates to irradiance. It does not recommend a dose, a wavelength, a device, or a condition to use one for, and it is not a claim that red light therapy treats anything.
Eye protection where the manufacturer specifies it, and medical advice for any condition, both come from sources other than a timer page. If you have a condition or take photosensitising medication, ask a clinician.
Arithmetic only: minutes required to deliver a target J/cm² at a given irradiance. Your device's irradiance at your working distance is the input that matters.
| Irradiance | For 3 J/cm² | For 6 J/cm² | For 10 J/cm² |
|---|---|---|---|
| 20 mW/cm² | 2:30 | 5:00 | 8:20 |
| 30 mW/cm² | 1:40 | 3:20 | 5:34 |
| 50 mW/cm² | 1:00 | 2:00 | 3:20 |
| 75 mW/cm² | 0:40 | 1:20 | 2:14 |
| 100 mW/cm² | 0:30 | 1:00 | 1:40 |
| 150 mW/cm² | 0:20 | 0:40 | 1:07 |
- J/cm² = mW/cm² × seconds ÷ 1000. Irradiance falls off sharply with distance, so a session length does not transfer between setups.
- The device's own instructions govern. This table converts a dose into minutes; it does not recommend a dose.
Sources
- Session lengths are direct arithmetic from irradiance and target energy density; no dose is recommended and device instructions are authoritative , TheTimerLab — accessed 2026-07-28