What you're drinking today
Add each drink with the time you have it. Defaults match real-world averages.
About you
Helps personalize FDA limit and metabolism speed.
Sleep impact
How much caffeine will still be active when you go to bed.
Caffeine in your system today
Want less caffeine without giving up coffee?
The ratio calculator shows you how to brew lighter cups — same volume, less caffeine.
Lower-caffeine alternatives
Swiss Water Process decaf
Chemical-free decaffeination that keeps the flavor. The benchmark for specialty decaf — under 5mg per cup.
See top decaf picks →Half-caf blends
Half regular, half decaf — cuts your caffeine in half without dropping a cup. Great for afternoons.
See half-caf options →100% Arabica light roasts
Arabica has roughly half the caffeine of Robusta. Light roasts often have slightly more, but a typical bag still lands ~80mg/cup.
See top Arabica beans →AeroPress for shorter brews
The shortest steep time of any method (1–2 min) means lower caffeine extraction — try ~70mg per cup with this method.
See AeroPress options →How caffeine moves through your body
What's a half-life and why does it matter?
Caffeine's half-life is how long it takes your body to eliminate half of what you consumed. The average healthy adult has a 5-hour half-life, but it ranges from 1.5 to 9.5 hours depending on genetics, smoking, contraceptives, pregnancy, and certain medications.
If you drink a 95mg cup at noon and you're a standard metabolizer:
5pm: ~48 mg still in your system
10pm: ~24 mg still in your system
3am: ~12 mg still in your system
That's why caffeine consumed even 6 hours before bed has been shown to disrupt sleep — research published in the Journal of Clinical Sleep Medicine found 400mg taken 6 hours before bedtime cut total sleep by over an hour. Most drinkers don't notice the difference subjectively, but measurements show it clearly.
Caffeine content by drink — the real numbers
These are typical ranges per serving for a standard cup size. Actual numbers vary with bean variety, roast, and brew strength.
8oz drip coffee: 80–100 mg
8oz pour-over: 80–120 mg
8oz French press: 80–135 mg
8oz AeroPress: 50–120 mg
1oz espresso shot: 63–75 mg
12oz cold brew: 150–240 mg
8oz cup of tea: 30–50 mg
12oz Coke: ~34 mg
12oz Red Bull: ~111 mg
16oz Monster Energy: ~160 mg
8oz decaf: 2–7 mg (yes, decaf has caffeine)
The biggest variables are cup size and brew method. A Starbucks Venti (20oz) drip coffee can easily hit 415mg — past the FDA daily limit in a single drink.
FDA limits — what they mean
The FDA considers up to 400 mg/day generally safe for healthy adults. That's roughly 4 standard cups of brewed coffee.
Pregnant women: ACOG recommends staying under 200 mg/day. Caffeine crosses the placenta and the fetus has limited ability to metabolize it.
Adolescents (under 18): The American Academy of Pediatrics recommends staying under 100 mg/day, and discourages caffeine entirely in children under 12.
Toxicity becomes a real risk above 1,000 mg in a short period. Powdered caffeine supplements are particularly dangerous — a teaspoon can contain a fatal dose.
How to time your last coffee for better sleep
Sleep researchers generally recommend keeping your bedtime caffeine level under 25 mg. Above that, caffeine measurably reduces sleep quality even if you fall asleep fine.
For a standard 5-hour half-life and a 95mg cup, that means cutting off coffee about 10 hours before bed. If you sleep at 11pm, your last cup should be by 1pm.
Slow metabolizers should cut off earlier (12+ hours before bed). Fast metabolizers can push it as late as 6 hours.
The use this calculator's "last safe coffee time" output reflects your inputs above — it adjusts for your bedtime, metabolism speed, and how big your typical cup is.
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