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Caffeine Calculator
Log your drinks and see how much caffeine is still in your body at bedtime — plus the last safe time to drink coffee.
What did you drink?
Your caffeine metabolism
Tap the drinks above to add them — results appear automatically.
How this works
Caffeine leaves your body exponentially, measured by its half-life — about 5.5 hours for most people. We assume a standard cup contains about 107 mg and treat 35 mg as the level at which sleep is mostly unaffected.
📖 Related reading: Caffeine and Sleep: How Coffee Affects Your Rest · Best Time to Sleep
Frequently asked questions
How long does caffeine stay in your system?
Caffeine has a half-life of about 5–6 hours in most adults.
How much caffeine is in a cup of coffee?
A brewed 8-oz cup has about 95–120 mg, a single espresso about 63 mg.
When should I stop drinking coffee before bed?
A practical rule: finish your last caffeinated drink about 9 hours before bedtime.
Disclaimer: This tool is for general informational purposes only and is not medical advice. If you have chronic sleep problems, please consult a healthcare professional.