Sleep & wake-up
Light exposure calculator
Enter your wake time to see when to get bright morning light to feel alert and steady your body clock.
Aim for 10-30 minutes of bright light within an hour of waking. Outdoors beats a window, and a window beats indoor lights.
Why morning light matters
Light is the strongest signal for your body clock. A dose of bright light soon after waking helps switch off the sleep hormone melatonin, lifts alertness, and tells your internal clock that the day has begun. Over time, consistent morning light nudges your rhythm earlier, which can make it easier to fall asleep at night and wake feeling refreshed.
| Light source | Rough brightness |
|---|---|
| Bright outdoors | very high |
| Overcast outdoors | high |
| Near a window | moderate |
| Indoor lighting | low |
How to get your dose
Aim for roughly ten to thirty minutes of light within about an hour of waking. Outdoors is best by far: even a grey, cloudy day is far brighter than a well-lit room. If you cannot get outside, sit by the brightest window you have. Pair the light with a short walk or breakfast so it becomes a habit. You do not need to stare at the sun; simply being out in daylight, with your eyes open, does the job.
Frequently asked questions
How much morning light do I need?
Around ten to thirty minutes within an hour of waking is a good target. Brighter light means you need less time, so a sunny morning outdoors works faster than a dim one.
Does light through a window count?
It helps, but far less than being outside. Glass blocks a lot of the intensity, so outdoor light, even when overcast, is much stronger and more effective at waking you up.
What if I wake before sunrise?
Use bright indoor light or a daylight lamp to get going, then catch real daylight as soon as the sun is up. Getting outside later in the morning still helps anchor your rhythm.