The short answer: 400 mg per day is a benchmark, not a goal
The U.S. Food and Drug Administration says that for most healthy adults, 400 mg of caffeine per day is an amount not generally associated with negative effects. That is roughly four or five cups of coffee only in the loosest sense, because coffee strength and serving size vary enormously. A large cold brew, energy drink, pre-workout, tea, soda, chocolate, and some medications or supplements can all contribute. The useful number is your total caffeine in milligrams across every source, not the number of “cups” you remember having.
“Too much” can happen below 400 mg
Four hundred milligrams is a population-level reference point, not a guarantee that 399 mg will feel fine. Caffeine sensitivity varies. Too much can show up as trouble sleeping, jitters, anxiety, a racing or pounding heartbeat, higher blood pressure, nausea, headache, or stomach upset. A single large dose can also feel very different from the same total spread earlier across the day. If your sleep or symptoms worsen at a lower intake, your useful personal limit is lower than the headline number.
Know your actual daily total before you decide what your limit should be.
Wellness Project keeps every caffeine dose and timestamp, adds the day up for you, and puts that history beside sleep, HRV, resting heart rate, recovery, and training so you can see your own pattern.
When a lower limit matters
Pregnancy is the clearest common example: the American College of Obstetricians and Gynecologists recommends keeping caffeine below 200 mg per day during pregnancy. Some medications and health conditions can also change how caffeine affects you or how quickly you clear it. Children and adolescents should not use an adult 400 mg benchmark as their target. If you have a heart rhythm issue, significant anxiety, pregnancy, or a medication interaction question, use guidance from your clinician rather than a generic internet limit.
The most useful caffeine limit is one you can compare with your own outcomes
A daily limit becomes more useful when you can answer three questions: how much caffeine did I actually have, when was the last dose, and what happened afterward? Wellness Project tracks the amount and time of individual doses, summarizes the daily total, and lets the same AI coaches that read your sleep, HRV, resting heart rate, recovery, workouts, and nutrition read the caffeine history too. That does not turn correlation into proof, but it gives you a much better starting point than guessing from memory.
Turn a generic caffeine limit into a pattern you can actually test.
Track the milligrams and the timing, then read them beside the sleep, HRV, recovery, nutrition, and training data you already collect.
