Caffeine Intake Calculator
Add up your daily caffeine from coffee, tea, energy drinks, and other sources. See how your intake compares to the FDA's 400 mg/day safe limit and your personal sensitivity.
Caffeine, the most used psychoactive drug in the world
Caffeine is consumed daily by 80-90% of adults worldwide. It works by blocking adenosine receptors in the brain, delaying the onset of fatigue and improving alertness, reaction time, and mood. In moderate doses (50-200 mg) it enhances cognitive performance and exercise capacity. At higher doses (above 400 mg/day in most adults, lower in slow metabolizers and pregnant women) it produces anxiety, insomnia, palpitations, and elevated blood pressure. The half-life averages 5 hours but ranges from 2 to 12 hours based on genetics (CYP1A2), pregnancy, oral contraceptives, and smoking.
How much caffeine is in your drink?
The classic 8 oz cup of brewed coffee contains about 95 mg of caffeine, but real-world values vary from 80 to 200 mg depending on bean variety, roast, grind, and brewing method. A single espresso shot has about 64 mg. Black tea delivers around 47 mg per 8 oz cup; green tea around 28 mg. Decaf is not caffeine-free, it still has 2-5 mg per cup. Energy drinks range from 80 mg (small can) to 300+ mg (large cans and shots). Even dark chocolate contains 12 mg per ounce.
The 400 mg/day ceiling, and who should aim lower
The FDA's 400 mg/day ceiling is based on decades of observational data showing no adverse health effects in healthy, non-pregnant adults below that threshold. However, several groups should aim lower. The American College of Obstetricians and Gynecologists recommends pregnant women stay under 200 mg/day to reduce miscarriage and low-birth-weight risk. The American Academy of Pediatrics recommends children and adolescents avoid caffeine entirely. People with anxiety disorders, arrhythmias, GERD, or uncontrolled hypertension often benefit from keeping intake under 200 mg/day.
Caffeine as an ergogenic aid
Caffeine is one of the few supplements with strong evidence for sports performance. A dose of 3-6 mg per kilogram of body weight taken 30-60 minutes before exercise improves endurance, power output, and focus. The benefit is largest in endurance sports (running, cycling, rowing) and smaller in pure strength events. Habitual users still benefit, though less than non-users. The downside: doses above 9 mg/kg can cause jitteriness, gastrointestinal distress, and elevated heart rate, and caffeine consumed after noon can disrupt sleep.
Formula sources, population limits, and references for this health risk calculator are documented in our public methodology. Read the methodology · Medical disclaimer