Caffeine Half-Life Calculator

Caffeine has an average half-life of about 5 hours — meaning half the caffeine you consumed is still in your system 5 hours later. At 10 hours, 25% remains. At 15 hours, about 12% remains. This varies based on genetics, liver enzymes, medications, and pregnancy (which can extend it to 15+ hours).

Espresso: 60–80mg · Filter/drip coffee (8oz): 80–120mg · Americano: 60–100mg · Cold brew (8oz): 100–200mg · Black tea: 40–70mg · Green tea: 20–45mg · Red Bull (8.4oz): 80mg · Monster (16oz): 160mg · Coca-Cola (12oz): 34mg.

Most sleep experts recommend stopping caffeine 6 hours before bedtime, but research suggests even 6 hours before bed reduces sleep time by over an hour. For optimal sleep, try stopping 8–10 hours before your target bedtime. If you sleep at 11pm, your last coffee should ideally be by 1–3pm.

Yes. Even if caffeine doesn't prevent you from falling asleep, it suppresses deep sleep and REM sleep throughout the night. Research shows 400mg of caffeine consumed 6 hours before bed still significantly reduces sleep quality, even in people who claim it doesn't affect them.