Blue-Light Exposure Calculator
See how much evening screen time falls inside the wind-down window before bed and get a screen-off cutoff to protect your melatonin.
How it works
Cutoff = bedtime − buffer · Exposure inside window = min(screen minutes, buffer) · Filter halves the risk score
Bright, blue-rich light in the evening tells your brain it is still daytime and can delay the rise of melatonin, pushing your body clock later. The minutes that matter most are the ones close to bed, inside your wind-down window, so this tool sets a screen-off cutoff and scores how much of your screen time lands inside it. Night-mode filters and blue-blocking glasses reduce the effect without removing it, which is why the risk is halved rather than zeroed — dimming the whole room and shortening late screen time do more than a colour filter alone.
Worked example
With an 11:00 PM bedtime and a 60-minute buffer, the screen-off cutoff is 10:00 PM. If 3 hours of screen time runs up to bedtime, 60 of those minutes fall inside the wind-down window — a high risk. Switching on a night filter halves the score into the moderate band.
Frequently asked questions
Do blue-light glasses actually help sleep?
Evidence is mixed. They cut some short-wavelength light, which may modestly help sensitive people, but overall light level and timing matter more. Dimming lights and stopping bright screens before bed is the higher-impact change.
Is it only blue light that matters?
No. Brightness and timing matter as much as colour. A dim warm screen late at night is gentler than a bright one, but any bright light close to bed can nudge your clock later.
How long before bed should I stop screens?
A buffer of 30–60 minutes is a common target. It gives melatonin room to rise and doubles as a wind-down cue, and the exact figure matters less than doing it consistently.
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Educational estimate only — not medical advice, diagnosis, or treatment. Individual needs vary; consult a qualified healthcare professional for decisions about sleep, hydration, nutrition, exercise, or ergonomics.