How Long Does Caffeine Stay in Your System?
Caffeine has a half-life of about 5 hours, which means half of what you drink at 2 p.m. is still in your system at 7 p.m. — and a quarter is still there at midnight. That residual is what blocks the adenosine signals your brain uses to make you sleepy. Pick what you drank or ate and when, and we'll show you how much caffeine you're bringing to bed.
Estimates only. Caffeine metabolism varies by genetics, medications, smoking, hormonal birth control, pregnancy, and age. Not medical advice.
What did you drink or eat?
Add each caffeinated item and roughly when you had it.
What's your target bedtime?
How quickly does your body process caffeine?
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Pick what you drank or ate above to see how much caffeine you're bringing to bed.
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Want a full picture of your sleep?
Caffeine is one of many factors. The College Sleep Score covers caffeine, environment, stress, schedule consistency, and more — in 5 minutes.
Take the College Sleep Score →How this works
Caffeine decays according to the formula caffeine_remaining = initial_dose × 0.5^(hours_elapsed / half_life), summed across all drinks. The default half-life of 5 hours reflects the documented average for healthy adults; the personalization options apply documented adjustments for smoking, hormonal birth control, pregnancy, and liver function. See the caffeine pillar for full references — Fredholm et al. 1999, Clark & Landolt 2017, Drake et al. 2013.
Product caffeine values are taken from manufacturer-published nutrition data wherever available. When manufacturer values disagree with retailer listings (this happens), we use the manufacturer value. Entries labeled "typical" (Other coffee shop drink, Other energy drink, etc.) are category averages drawn from the FDA, the American Beverage Association, and aggregated industry data — use these when your specific product isn't in the list. For a precise value, use the Custom amount option.
Last updated June 1, 2026. 54 products in current database.
We collect anonymous usage data — which drinks were picked, calculation results, and your optional education stage — to improve the tool and write better content. No personal information is collected or stored. See our privacy policy for more.