Sleep & wake-up
Blue light cutoff calculator
Enter your bedtime to see when to put bright screens away so blue light does not hold back your sleep.
Bright screens in the evening can suppress melatonin. A cutoff about 90 minutes before bed gives your body time to wind down.
Why blue light affects sleep
Light in the blue part of the spectrum, which phones, tablets and laptops give off strongly, is a powerful signal to your body clock. In the evening it can suppress melatonin, the hormone that readies you for sleep, and push your internal clock later. Cutting bright screens before bed gives melatonin room to rise. This tool sets a cutoff about 90 minutes before your bedtime so your brain has time to shift into wind-down mode.
| Time before bed | What to do |
|---|---|
| About 90 minutes | Stop bright screens or switch to dim, warm light |
| 60 minutes | Lower room lighting and avoid stimulating content |
| At bedtime | Screens off, room dark and cool |
If you must use screens
A hard cutoff is ideal, but not always realistic. If you need a device late, turn on night mode or a warm colour filter, lower the brightness as far as is comfortable, and hold it further from your face. Swapping a bright overhead light for a dim, warm lamp helps too. The goal is less bright light reaching your eyes in the last stretch before sleep, not perfection.
Frequently asked questions
Why 90 minutes before bed?
It gives melatonin time to rise without bright light holding it back. Ninety minutes is a practical window that suits most routines; earlier is better if you can manage it.
Do night mode and blue light filters help?
They reduce the blue light reaching your eyes, which helps, but brightness and engaging content still keep your brain alert. Dimming the screen and avoiding stimulating apps matter as much as the colour filter.
What should I do instead of scrolling?
Swap screens for calmer wind-down activities such as reading on paper, light stretching, a warm shower or quiet music under dim, warm lighting. These help signal to your body that sleep is coming.