Caffeine Overdose Calculator

Calculate your safe caffeine intake based on your personal factors

Personal Info & Preferences
Vol:
Wt:
Female Health Status
Your Safe Caffeine Limit:
400 mg
Daily Caffeine Consumption Tracker
Tracked Items
Item Size Qty Caffeine mg
Total Caffeine 0 mg
Your Caffeine Level
0 Safe Caution Danger
Recommendations vary by health status. Consult a doctor for personal advice.

How this calculator works

The figure in the panel above is not the FDA's 400 mg reprinted. It is built in three steps.

1. An age and status baseline. Adults start at 400 mg a day, the level the FDA cites as not generally associated with negative effects. Over-65s start at 300 mg, 13-17s at 100 mg, and under-13s at zero. Tick Pregnant and the baseline drops to 200 mg, the ceiling in ACOG's committee opinion; Breastfeeding sets 300 mg.

2. Your body weight. The tool multiplies your weight by 6 mg/kg for adults, 4.5 mg/kg for over-65s and 2.5 mg/kg for teenagers, then uses that number whenever it comes out below the baseline. A 55 kg adult is capped at 330 mg rather than 400. For teenagers the weight-based figure always wins. For reference, EFSA puts habitual daily intake at 5.7 mg/kg and single doses at 3 mg/kg, so the adult factor used here is marginally the more permissive of the two.

3. Your sensitivity. The five-point sensitivity setting applies a multiplier running from 1.3x on Low down to 0.7x on Extreme. This is the one step with no guideline behind it: it is a self-reported adjustment, and on Low it can return a number above 400 mg. Read anything over 400 mg as a personal estimate, not as permission - the official ceilings do not move with a slider.

The meter then scores your tracked drinks against that limit: green to 50%, amber to 100%, red above it.

How much caffeine is in your drink?

Every figure below comes from the manufacturer's own nutrition data or from the FDA. Where a brand publishes a range, the range is shown rather than an average.

Drink Serving Caffeine Source
Brewed coffee (generic)
The FDA's own working figure for one cup. Real cups vary widely with grind, dose and brew time. 		8 fl oz (237 ml) 80-100 mg FDA, Spilling the Beans: How Much Caffeine is Too Much?
Tea (generic, black or green)
Steeping time moves this more than leaf type does. 		8 fl oz (237 ml) 30-50 mg FDA, Spilling the Beans: How Much Caffeine is Too Much?
Pike Place Roast brewed coffee, Grande
Starbucks publishes a range, not a point value. The top of it is most of an adult daily limit in one cup. 		16 fl oz (473 ml) 315-390 mg Starbucks published nutrition
Caffè Latte, Grande
Two espresso shots. Less than half a same-size brewed coffee, because the cup is mostly milk. 		16 fl oz (473 ml) 150 mg Starbucks published nutrition
Cold Brew, Grande
A 20-hour cold steep extracts more than a hot brew of the same size would in minutes. 		16 fl oz (473 ml) 205 mg Starbucks published nutrition
Red Bull Energy Drink
The reference point most people misjudge: a standard can has less caffeine than a small brewed coffee. 		8.4 fl oz (250 ml) 80 mg Red Bull product Q&A
Monster Energy Original
Also contains guarana, which is itself a caffeine source; the 160 mg is the all-sources figure on the label. 		16 fl oz (473 ml) 160 mg Monster Energy product page
Celsius Energy Drink
Celsius itself recommends no more than two cans a day, which is 400 mg - the entire adult guideline. 		12 fl oz (355 ml) 200 mg Celsius Essential Facts
Celsius Essentials
Celsius recommends one can a day of this line, not two. 		16 fl oz (473 ml) 270 mg Celsius Essential Facts
Alani Nu Energy Drink
200 mg in a 12 oz can that drinks like a soda. Half the adult daily guideline per can. 		12 fl oz (355 ml) 200 mg Alani Nu nutrition facts
Coca-Cola Classic 12 fl oz (355 ml) 34 mg The Coca-Cola Company, ingredients FAQ
Diet Coke
More caffeine than regular Coke, which surprises most people. 		12 fl oz (355 ml) 46 mg The Coca-Cola Company, ingredients FAQ
Pepsi 12 fl oz (355 ml) 38 mg PepsiCo Product Facts
Mountain Dew
The most caffeinated mainstream soda, and still a third of a Celsius. 		12 fl oz (355 ml) 54 mg PepsiCo Product Facts
Cola soft drink (generic) 8 fl oz (237 ml) 40 mg FDA, Spilling the Beans: How Much Caffeine is Too Much?
5-hour Energy, Regular Strength
200 mg in under two fluid ounces. Volume tells you nothing about dose here. 		1.93 fl oz (57 ml) 200 mg 5-hour Energy, Regular Strength FAQ
Caffeine tablet
Two coffees' worth with none of the volume cues that normally pace you. This is the format most often involved in accidental overdose. 		1 tablet 200 mg FDA, Spilling the Beans: How Much Caffeine is Too Much?

Figures verified September 2026. Brands reformulate; check the can if the number matters to you.

What this calculator does not account for

Weight, age and a sensitivity setting are the inputs most people can supply accurately. They are not the only things that decide how caffeine behaves in you.

  • CYP1A2 genetics. Nearly all caffeine is cleared by one liver enzyme, and its activity varies across the population with a coefficient of variation of roughly 40% (clinical toxicology review). Two people of identical weight can clear the same cup at very different rates.
  • Medications. Oral contraceptives, ciprofloxacin, cimetidine and fluvoxamine all inhibit CYP1A2 and slow caffeine clearance (same review). Nothing in the form above knows what you take.
  • Smoking. Smoking induces CYP1A2 and speeds clearance by about 40-65%, with reported half-life falling from around 6 hours to 3.5 (2025 review).
  • Liver disease and anxiety disorders. The first slows clearance; the second changes what a tolerable dose feels like, well below any toxic threshold.
  • Timing. This is a daily total, not a timeline. 400 mg spread over a day and 400 mg in one sitting are not the same exposure, and caffeine's mean half-life of about five hours (NCBI) means an afternoon coffee is still measurably present at bedtime.

Common questions

How much caffeine is too much?

For most healthy adults the FDA cites 400 mg a day as an amount not generally associated with negative effects - roughly two to three 12 oz cups of coffee. EFSA puts the same ceiling at about 5.7 mg per kg of body weight, and adds a 200 mg limit for any single dose. Below those figures you are in the range the evidence supports; above them you are past what regulators are willing to call safe.

How long does caffeine stay in your system?

Caffeine's mean half-life in healthy adults is about five hours, but individual half-lives range from roughly 1.5 to 9.5 hours. On a five-hour half-life, a 200 mg coffee at 3pm still leaves about 50 mg circulating at 11pm. Pregnancy, liver disease and drugs such as oral contraceptives and ciprofloxacin lengthen that; smoking shortens it.

How much caffeine is safe during pregnancy?

ACOG's committee opinion concludes that moderate consumption under 200 mg a day does not appear to be a major contributing factor in miscarriage or preterm birth, and 200 mg is the figure this calculator applies when you tick Pregnant. That is about one 12 oz cup of coffee - or less than one 12 oz can of Celsius or Alani Nu.

What are the signs of too much caffeine?

Jitteriness, a racing or irregular heartbeat, insomnia, headache, nausea and anxiety are the common early signs. Vomiting, chest pain, confusion, seizures or a heart rate that will not settle are emergency signs - call poison control or your local emergency number rather than waiting them out.

Does the 400 mg limit apply to everyone?

No. It is a population figure for healthy adults. It does not apply to under-18s, to pregnancy, or to anyone with a cardiac arrhythmia, an anxiety disorder or liver disease. It also assumes average caffeine clearance, and clearance varies across the population by roughly 40% because CYP1A2 enzyme activity does. Body weight matters too: 400 mg in a 50 kg adult is a far larger dose per kilogram than in a 90 kg one.

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