Caffeine Calculator
Caffeine sneaks up in sums: two filter coffees, an afternoon cola and a pre-workout energy drink land you at 284 mg before anything with a shot count. This calculator lists the nine most common sources with their typical milligrams — pick how many of each you've had and the total appears against the 400 mg daily guideline for healthy adults.
The second stat answers the sleep question: caffeine's half-life is roughly 5-6 hours, so the tool prints a last-safe-cup time for an 11 PM bedtime. The countdown logic pairs naturally with the sleep cycle calculator — and because the page remembers your usual picks, tomorrow's tally is two taps instead of a memory test.
How to use
- Select how many of each drink you've had today — the total updates against the 400 mg guideline.
- Check the cutoff stat for the last cup that won't fight your 11 PM bedtime.
- Share the tally with one tap, or bookmark it — the page remembers your picks.
Frequently asked questions
How much caffeine is safe per day?
Up to 400 mg daily is the guideline for healthy adults — about four filter coffees — and single doses stay under 200 mg. Pregnancy, some medications and heart conditions lower the ceiling substantially; the calculator's remaining-total stat assumes the standard 400 mg.
How long does caffeine stay in your system?
Half-life averages 5-6 hours: 100 mg at 4 PM leaves about 50 mg at 10 PM and 25 mg at 4 AM. That residual is enough to lighten sleep even when you fall asleep normally, which is why the cutoff stat works backwards from bedtime.
How much caffeine is in a cup of coffee?
A filter or drip cup runs ~95 mg, an espresso shot ~63 mg, instant ~66 mg, black tea ~47 mg, green tea ~28 mg, cola ~34 mg per 330 ml, and a 250 ml energy drink ~80 mg. Actual figures vary by bean, brew and brand — the calculator uses these widely-cited averages.
Does decaf or matcha count?
Decaf is not zero — about 7 mg per cup, worth counting if you drink several. Matcha and green tea carry meaningful caffeine with a slower ramp from L-theanine; the calculator includes both so tea drinkers get an honest total too.