Lux levels chart: sunlight, rooms and screens

How many lux is sunlight?

Looking at a bright blue midday sky gives more than 100,000 lux, while typical indoor lighting sits around 200 lux.² Real readings depend on where the meter points. In a study in Hyderabad, India, a meter held at eye level in an open playground read a median of 14,350 lux across the day, topping out at 93,500.⁴ Tree shade had a median of 1,580 lux, and the three most open sites still gave 1,150 lux on cloudy days. That is brighter than most rooms.

How the lux levels chart works

Each bar is a typical illuminance taken from a measurement study or a standard, with its source numbered. The scale is logarithmic because light spans about six orders of magnitude, from moonlight to midday sun. On a straight scale every indoor setting would be a sliver next to sunlight.

The lighter bands show spread. For the Hyderabad rows that is the middle half of readings; for moonlight it is the typical range up to an upper limit of about 0.3 lux, based on measurements of a supermoon.³

Lux vs melanopic EDI

Lux weights light by how bright it looks to the cones you see with. Your body clock gets most of its input from melanopsin cells in the retina, which respond best to shorter, bluer wavelengths. A 2014 review by 14 light researchers concluded that photopic lux is inadequate for measuring light's effects on the body clock and other non-visual responses.⁸

Melanopic EDI (equivalent daylight illuminance) fixes that. It is the lux of standard daylight that would stimulate melanopsin as much as the light you are under.¹ For daylight, 1 lux is about 1 melanopic EDI lux. Electric light gives less. Many warm white LEDs (2700 to 3000 K) have a melanopic ratio below 0.35, office lamps at 3000 to 4000 K below 0.6, and one 6500 K tunable LED 0.83.¹

The three targets on the chart

In 2022 an international group of researchers published recommendations for healthy adults, measured at the eye with the sensor vertical, about 1.2 m off the floor:¹

• Daytime: at least 250 melanopic EDI lux. Daylight should be used first where it is available.
• Evening, from at least 3 hours before bed: no more than 10.
• Sleep: no more than 1, or 10 if you need to see during the night.

Evening homes typically measure around 30 lux, so warm white LEDs can meet the evening limit without much dimming. Offices that just meet the 500 lux desk standard usually give less than 200 melanopic EDI lux at the eye across the day, short of the daytime target.¹

How the reading checker works

1. It multiplies your lux reading by the melanopic ratio for the light you pick to estimate melanopic EDI.
2. It sorts the time into day, evening (the 3 hours before your bedtime) or sleep (bedtime to wake time). It uses your device's clock time, so bedtimes after midnight and daylight saving changes work.
3. It compares the estimate with the target for that period and tells you what meter reading would meet it with the same light.

Assumptions and limits

• Hold the meter at eye level with the sensor facing where you look. Lighting standards measure on the desk, facing up, which can read very differently.
• The ratios for warm and neutral white are upper bounds from Brown et al., and the cool white figure comes from one LED. Your lamp may be lower, so the checker can overstate melanopic light. In the evening that errs on the safe side; during the day you may fall short even when it says you pass.
• Lux meters vary widely in how they respond across the spectrum, so two meters can disagree under the same lamp.⁶
• Several chart rows come from one tropical city. Weather, season, time of day and meter direction all change the numbers.⁴
• The phone figure is a worst case: full white screen, maximum brightness, 15 cm away. The evidence on whether phone use in the evening matters in practice is inconclusive.⁵
• 10,000 lux at 30 to 33 cm is the standard light therapy dose.⁶ Bright light can trigger hypomania in people with bipolar disorder, so talk to a doctor first if that applies to you. See how to use a SAD lamp.

To measure your own space, see the lux meters we compare, or plan outdoor time with the daylight planner.

Sources

1. Brown TM, Brainard GC, Cajochen C, et al. Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults. PLoS Biol. 2022;20(3):e3001571. doi:10.1371/journal.pbio.3001571
2. Wright KP Jr, McHill AW, Birks BR, et al. Entrainment of the human circadian clock to the natural light-dark cycle. Curr Biol. 2013;23(16):1554–1558. doi:10.1016/j.cub.2013.06.039
3. Kyba CCM, Mohar A, Posch T. How bright is moonlight? Astron Geophys. 2017;58(1):1.31–1.32. doi:10.1093/astrogeo/atx025
4. Bhandary SK, Dhakal R, Sanghavi V, Verkicharla PK. Ambient light level varies with different locations and environmental conditions: potential to impact myopia. PLoS One. 2021;16(7):e0254027. doi:10.1371/journal.pone.0254027
5. Schlangen LJM, Price LLA. The lighting environment, its metrology, and non-visual responses. Front Neurol. 2021;12:624861. doi:10.3389/fneur.2021.624861
6. Terman M, Terman JS. Light therapy for seasonal and nonseasonal depression: efficacy, protocol, safety, and side effects. CNS Spectr. 2005;10(8):647–663. doi:10.1017/S1092852900019611
7. National Institute of Standards and Technology. NIST Guide to the SI, Appendix B.8: Factors for units listed alphabetically (footcandle to lux). nist.gov
8. Lucas RJ, Peirson SN, Berson DM, et al. Measuring and using light in the melanopsin age. Trends Neurosci. 2014;37(1):1–9. doi:10.1016/j.tins.2013.10.004

General information, not medical advice.