Melanopic EDI Calculator
Light level matters. So does spectrum.
Alongside visual comfort and task lighting, consider the light reaching your eyes. Explore how spectrum and dimming shape melanopic EDI: meet daytime targets with fewer eye-level lux, or retain more light within evening and nighttime limits.
What is melanopic EDI?
Melanopic equivalent daylight illuminance (mEDI) expresses melanopic light exposure relative to standard daylight (D65). It depends on both the spectrum and the light reaching your eyes.
mEDI = eye-level illuminance × mDER
mDER describes the spectrum’s melanopic effectiveness per lux. Ev is vertical illuminance at the modelled eye point ; Eh is average horizontal illuminance over the shown calculation area. Eh is not used to calculate mEDI.
Different tasks. Different spectra.
Setup and Alternative are two editable choices for the same room, not a ranking of products.
Daytime: a higher mDER can reach the daytime target with fewer eye-level lux. Before bed: a lower mDER can allow more lux within the evening limit.
Brown et al. (2022) recommend ≥250 mEDI lx during the day, ≤10 for at least three hours before bed, and ≤1 during sleep, for healthy adults with regular daytime schedules. Necessary nighttime activities have a separate ≤10 recommendation. The corridor opens at the stricter sleep-level target; switch to ≤10 to explore nighttime activity. “Target met” refers only to the selected mEDI threshold. It does not confirm visual comfort, safe movement or a complete lighting design.
Make this work in your space.
Open either setup to see its components and dimensions, then request a quotation and a calculation for your project.
Component schedules require final electrical, thermal and installation checks.
Questions about melanopic light
How is mEDI different from ordinary lux?
Photopic lux describes light weighted for daytime visual sensitivity. mEDI uses melanopic sensitivity and a daylight reference. Two sources can deliver the same lux but different mEDI because their spectra differ.
Where should I measure the light?
At the eye, with the receiving plane vertical and facing the usual viewing direction for these seated or standing scenarios. The calculator also shows the familiar horizontal illuminance (Eh) on the room plane or floor, but there is no fixed conversion from Eh to eye-level illuminance, and Eh is not used to calculate mEDI.
Are the targets standards or recommendations?
Brown et al. (2022) recommend ≥250 lx mEDI during daytime, ≤10 in the three hours before bed and ≤1 in the sleep environment for healthy adults. For nighttime activities requiring vision, their recommendation is ≤10. The nighttime corridor opens at the stricter sleep-level ≤1 goal; switch to ≤10 to explore nighttime activity. Neither goal certifies visibility, safe movement or compliance.
Does colour temperature tell me the mDER?
No. Sources with similar CCT can have different spectra and mDER. This calculator uses measured spectra rather than estimating mDER from Kelvin alone.
Can this replace a lighting calculation for my project?
No. The three rooms are worked examples: their eye-level illuminance comes from lighting calculations for these specific rooms, fixtures and eye positions. Your project needs its own calculation with your geometry, surfaces, fixtures, other light sources and viewing positions.
Metric definition: CIE S 026:2018 ↗ · Exposure recommendations: Brown et al. (2022) ↗
Yuji · Premium LED Solutions — CIE spectral data — CIE reference data © CIE 2018/2019 · CC BY-SA 4.0
How this calculator works
Room calculations provide photopic illuminance; measured source spectra provide mDER. Intermediate settings and relative dimming output are modelled. Source spectra approximate the spectrum at the eye; spectral changes from covers and room reflections are not modelled. The images illustrate the room, not calibrated brightness or visibility. Results describe one eye position and the shown lighting only; daylight, extra sources, exposure duration and individual responses are not assessed. Surface lux values are descriptive, not a compliance check. Brown’s daytime/evening reference is approximately 1.2 m at the eye; this model uses seated and standing heights shown in Calculation details. The sleep environment should be as dark as possible; the corridor is not a bedroom assessment.
For a calculation tailored to your project, .