Lifestyle
Food & Nutrition
FitnessFind your safe daily caffeine limit and what it equals in drinks.
This tool is for general information only and is not medical advice. Talk to a healthcare professional about results that concern you.
How Much Caffeine Is Safe Per Day?
For healthy adults, the FDA and the European Food Safety Authority put the safe ceiling at about 400 mg of caffeine a day, roughly four cups of brewed coffee, with no more than about 200 mg in a single sitting. Because caffeine is dosed by body weight (around 5.7 mg per kg per day), smaller people hit their limit sooner, which is what this calculator accounts for.
Pregnancy changes the math: guidance from ACOG and EFSA caps intake at 200 mg a day, because caffeine crosses the placenta and is cleared much more slowly during pregnancy. Teenagers should stay around 100 mg, and people who feel jittery on small amounts are usually slow metabolizers, a genuine genetic difference, and do better at half the standard limit.
The Timing Rule That Matters Most
Caffeine has a half-life of about five hours, so half of your 4 pm coffee is still circulating at 9 pm, and a quarter at 2 am. It does not just delay sleep; it cuts deep sleep even when you fall asleep fine. The practical rule: last caffeine at least 8 hours before bed. If you sleep at 11 pm, that means nothing after 3 pm. Our sleep calculator pairs naturally with this one.
Signs You Are Over Your Limit
- Jitters, racing heart, or anxiety in the hours after drinking
- Needing caffeine to avoid a headache (dependence, not energy)
- Waking at 3 am wired despite being exhausted
- An afternoon crash that sends you back for more
Frequently Asked Questions
Is coffee bad for you?
At normal doses, the research runs the other way: moderate coffee drinking is associated with lower risk of type 2 diabetes, liver disease, and Parkinson’s. The problems come from dose, timing, and what gets added to the cup.
How long does caffeine stay in your system?
Half is gone in about 5 hours, but full clearance takes over a day. Genetics swing this widely: fast metabolizers clear it in half the time of slow ones, which is why the same latte treats two people so differently.
Does caffeine dehydrate you?
Not at normal intakes. The mild diuretic effect is smaller than the fluid the drink provides, so coffee and tea count toward your daily fluids. Our water calculator includes them.
How do I cut back without headaches?
Taper instead of quitting cold. Drop by half a cup every few days, or swap one coffee for tea. Withdrawal headaches peak around day two of abrupt stops and are mostly avoidable with a one to two week taper.
Sources
- Spilling the Beans: How Much Caffeine is Too Much? · FDA
- Caffeine · EFSA
- How much coffee can I drink while I'm pregnant? · ACOG
- Caffeine – StatPearls – NCBI Bookshelf · NIH (NCBI Bookshelf)
This calculator is for general information only. If you have a heart condition, anxiety disorder, or are pregnant, discuss caffeine with your doctor.