Up to 400 mg of caffeine a day — about four small brewed coffees — is considered safe for healthy adults, and 200 mg in pregnancy. Caffeine has a half-life of about 5 hours, so half of an afternoon coffee is still circulating at bedtime. This free calculator totals your real daily intake across coffee, tea, energy drinks and chocolate.
Caffeine is the world’s most used stimulant, and almost nobody knows their actual daily dose. This caffeine calculator adds up what you really consume — coffee, tea, energy drinks, cola, chocolate — and compares it with the evidence-based safe limit, so “a few coffees” becomes a number you can judge.
Track your intake below, then read on: how much caffeine is too much, how long caffeine really lasts in your system (the half-life math surprises most people), and what is actually in each drink.
Daily Caffeine Tracker
Compare your intake against the safe daily limit.
How much caffeine is too much?
The consensus from the FDA and European food safety authorities: up to 400 mg per day is not associated with harm in healthy adults — roughly four small cups of brewed coffee. Lower limits apply where they matter most:
- Pregnancy and breastfeeding: maximum 200 mg/day (ACOG guidance).
- Adolescents: ideally under 100 mg/day; energy drinks are the usual overshoot.
- Sensitive individuals — anxiety disorders, reflux, arrhythmias, uncontrolled high blood pressure — often need personal limits well below 400 mg, set with their physician.
Signs you are over your own threshold: jitteriness, anxiety, palpitations, upset stomach, and — most tellingly — poor sleep even when the last cup was at lunch.
Caffeine half-life: the math your sleep already knows
Caffeine’s half-life is about 5 hours in typical adults (range 3–7 depending on genetics, liver function, smoking, pregnancy and some medications). Half-life means half is still circulating after that time — and the decay keeps going:
| Time after a 200 mg coffee | Caffeine still in your system |
|---|---|
| 0 hours | 200 mg |
| 5 hours | 100 mg |
| 10 hours | 50 mg |
| 15 hours | 25 mg |
| 20 hours | 12–13 mg |
A 4 pm double espresso leaves a third of its caffeine on board at 11 pm — enough to cut deep sleep even in people who “fall asleep fine”. The practical rule: keep caffeine at least 8 hours from bedtime, and pair this tool with our sleep calculator if mornings are a struggle.
Caffeine content in drinks
| Drink | Serving | Typical caffeine |
|---|---|---|
| Brewed filter coffee | 240 ml (8 oz) | ~95 mg |
| Espresso | Single shot (30 ml) | ~63 mg |
| Instant coffee | 240 ml | ~60 mg |
| Turkish coffee | 60 ml cup | ~50–65 mg |
| Black tea | 240 ml | ~47 mg |
| Green tea | 240 ml | ~28 mg |
| Energy drink | 250 ml can | ~80 mg (large cans 150–300 mg) |
| Cola | 330 ml can | ~32–40 mg |
| Dark chocolate | 30 g | ~20–25 mg |
| Decaf coffee | 240 ml | ~2–5 mg |
Real-world servings drift far above these baselines — a large coffee-shop brew can carry 200–300 mg on its own, which is how “two coffees a day” quietly becomes 500 mg.
Caffeine and your heart, blood pressure and stomach
Moderate coffee intake is, by current evidence, neutral-to-mildly-protective for cardiovascular health in most people. Caffeine does raise blood pressure acutely for a few hours — relevant if yours is uncontrolled — and can trigger palpitations or reflux in the susceptible. Anyone with an arrhythmia, uncontrolled hypertension or pregnancy should agree a personal limit with their doctor rather than defaulting to 400 mg.
Caffeine and performance: the one supplement that works
Caffeine is among the best-evidenced performance aids in sports science: 3–6 mg per kilogram taken 30–60 minutes before exercise improves endurance, sprint output and perceived effort across hundreds of trials — for a 70 kg person, roughly 200–400 mg, i.e. strong coffee, no exotic products required. The honest fine print: mental sharpness benefits appear at far lower doses (even 40–100 mg); habitual users keep most of the ergogenic effect (abstaining for days before a race is largely unnecessary suffering); responders vary genetically; and the dose that helps a morning race wrecks an evening one’s recovery sleep — the half-life math from above doesn’t pause for sport.
Tolerance: why coffee “stops working”
Caffeine works by blocking adenosine — the sleepiness molecule — at its receptors. The brain’s counter-move is simply building more receptors, so within 1–3 weeks of steady intake, your usual dose mostly cancels the withdrawal it created, rather than lifting you above baseline. That is the treadmill behind escalating consumption. The reset is mercifully quick: receptor numbers renormalize within roughly 1–2 weeks of reduced intake, restoring sensitivity — which is why an occasional “caffeine holiday”, or simply holding a modest steady dose, keeps the effect honest. Alertness architecture works better than dose escalation: caffeine after (not instead of) sleep, and before the daily dip, not all day long.
Decaf and the alternatives, honestly rated
For trimming intake without losing the ritual: decaf is genuinely low (2–5 mg per cup) with coffee’s taste and antioxidants intact — the strongest swap; green and herbal teas step down gradually (28 mg → 0), with rooibos and mint truly caffeine-free; L-theanine, tea’s calming amino acid, is why tea’s caffeine feels smoother than coffee’s spike — the combination is well studied for calm alertness. Watch the imposters: “energy” products with guarana or yerba mate are simply caffeine wearing a costume (guarana is caffeine-dense by weight), and pre-workout powders routinely pack 150–300 mg per scoop — counted, per the calculator above, like everything else.
Cutting back without the headache
Caffeine withdrawal — headache, fatigue, irritability — peaks a day or two after stopping abruptly and can last most of a week. The evidence-backed exit is gradual: reduce by about half a cup every few days, swap late-day cups for decaf or green tea first (protecting sleep pays immediately), and hold your last caffeine of the day progressively earlier. Most people land comfortably at 100–200 mg without missing the rest.
This tool is informational. It does not replace medical advice — particularly in pregnancy, heart rhythm disorders or uncontrolled blood pressure, where your right limit is personal.
Frequently asked questions
How much caffeine per day is safe?
Up to 400 mg daily for healthy adults, and up to 200 mg in pregnancy. Individual tolerance varies widely — sleep quality and jitteriness are your personal feedback.
How long does caffeine stay in your system?
With a ~5-hour half-life, half remains after 5 hours and a quarter after 10. It takes roughly a full day for a dose to clear almost completely.
How many cups of coffee is 400 mg?
About four 240 ml cups of brewed filter coffee — but only two large coffee-shop brews, which is why counting milligrams beats counting cups.
Does caffeine raise blood pressure?
Acutely yes, by a few mmHg for 2–3 hours, more in irregular users. Habitual moderate intake shows little lasting effect in most people, but uncontrolled hypertension warrants a personalized limit.
Why does coffee at noon still ruin my sleep?
Slow metabolizers — a genetic trait — can carry an effective dose into the night even from midday coffee. If sleep is poor, try a 10-day trial with the last cup before 10 am.
Is caffeine addictive?
It produces dependence with a real withdrawal syndrome (headache, fatigue) but not addiction in the clinical sense. Tapering over a week avoids most withdrawal symptoms.
Why doesn’t coffee affect me anymore?
Receptor tolerance — steady intake grows more adenosine receptors until your dose mostly cancels its own withdrawal. One to two weeks at a lower dose resets sensitivity.
How much caffeine before a workout?
The evidence-based range is 3–6 mg/kg taken 30–60 minutes before — about 200–400 mg for a 70 kg adult. Time it so the half-life math doesn’t collide with your bedtime.
Does decaf have caffeine?
A little — typically 2–5 mg per cup versus ~95 mg in regular brew. Even several decafs stay far below meaningful doses, which makes it the best evening swap.
Numbers are a starting point — not a diagnosis
If your results raise questions, Acibadem specialists can review your situation properly: share your case and receive a free, no-obligation medical opinion from the relevant department.