Melanopic Lux Calculator: Light & Sleep Timing Planner

Light & sleep tool

Melanopic Lux & Sleep-Pressure Timing Calculator

Estimate the melanopic equivalent daylight illuminance (melanopic EDI) reaching your eyes, then build a simple light-and-sleep timing plan around your usual wake-up and bedtime.

Important: this is an educational planning tool, not a diagnostic test. It cannot measure your personal melatonin, cortisol, circadian phase or “sleep pressure”.

1. Melanopic EDI calculator

Use a light level measured at eye level, ideally with a meter or a manufacturer’s lighting report. Ordinary room lux alone is not enough: spectrum matters.

Photopic illuminance at the eye (lux)

Enter the light level at your eyes, not the lamp’s advertised lumens.

Melanopic daylight efficacy ratio (MDER)

Use the manufacturer’s MDER where available. Melanopic EDI ≈ photopic lux × MDER.

Quick, illustrative presetUse my own MDERDaylight / D65 reference (1.00)Cool-white LED — rough example (0.90)Neutral-white LED — rough example (0.70)Warm-white LED — rough example (0.45)

These are broad illustrations only. CCT does not determine melanopic EDI on its own.

Enter your figures and select Estimate melanopic EDI.

2. Light & sleep timing planner

This planner uses the widely cited consensus framework for healthy adults with regular daytime schedules: brighter days, substantially dimmer evenings, and darkness during sleep.

Usual wake-up time

Usual bedtime

Your usual sleep need (hours)

Add your normal times and select Build my timing plan.

What the numbers mean

Melanopic EDI is a standardised way to describe how strongly a light source stimulates melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs), relative to daylight. These cells contribute to circadian timing, alertness and pupil responses; they are not separate from vision in the simplistic sense.

Time of day	Consensus reference for healthy adults	Practical meaning
Daytime	At least 250 melanopic EDI lux	Prioritise outdoor daylight or bright indoor light, especially earlier in the day.
Evening (start ≥3 hours before bed)	No more than 10 melanopic EDI lux	Lower room brightness and avoid direct, blue-enriched light where possible.
During sleep	No more than 1 melanopic EDI lux	Keep the bedroom dark; if you need light, use only what is necessary for safety.

These are population-level consensus recommendations, not a treatment prescription. Age, eye health, shift work, medicines, psychiatric conditions and sleep disorders can all change what is appropriate.

About “sleep pressure”: sleep pressure is the homeostatic drive to sleep that generally grows while you are awake and falls during sleep. The calculator reports time awake as a simple proxy; it cannot quantify the biological process. Light chiefly helps time the circadian clock, rather than directly “calculating” or eliminating sleep pressure.

Melanopic lux FAQs

Can I calculate melanopic lux from phone brightness or bulb wattage?

Not reliably. You need the spectrum and the amount of light arriving at the eye. A product’s lumen output, wattage, screen setting or colour temperature is not enough on its own.

Is blue light always bad for sleep?

No. Short-wavelength-rich light can be useful in daytime, when it supports alertness and circadian timing. In the evening, the same kind of light is more likely to delay the body clock or reduce melatonin, especially when it is bright, close to the eyes and used late.

Should I use this tool if I have insomnia or work night shifts?

Use it only as general education. For persistent insomnia, major daytime sleepiness, suspected sleep apnoea, bipolar disorder, eye disease, or shift-work problems, ask a GP, optometrist or sleep professional for personalised advice.

Sources: CIE S 026 framework for α-opic light measurements; Brown et al., 2022, PLOS Biology, consensus recommendations for indoor daytime, evening and night-time light exposure. Read the open-access consensus paper.