Caffeine Calculator
Daily caffeine intake and safe limit.
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Add up the caffeine hiding in your day — coffees, teas, colas, energy drinks, even dark chocolate — and see where you stand against the general safe limit. It also estimates how long the caffeine will take to clear before bed.
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Caffeine — The Quick Answer
Up to about 400 mg of caffeine a day is considered safe for most healthy adults — roughly four 240 ml cups of brewed coffee. It has a half-life of 4–6 hours, so an afternoon coffee lingers well into the night.
Shortcut
Safe limit ≈ 400 mg/day (adults); ~200 mg during pregnancy
Caffeine in common drinks
| Source | Serving | Caffeine |
|---|---|---|
| Brewed coffee | 240 ml | ~95 mg |
| Espresso | 30 ml | ~63 mg |
| Instant coffee | 240 ml | ~62 mg |
| Black tea | 240 ml | ~47 mg |
| Green tea | 240 ml | ~28 mg |
| Cola | 355 ml | ~34 mg |
| Energy drink | 250 ml | ~80 mg |
Caffeine content varies widely with bean, roast, brewing method, and cup size — a large café coffee or strong home brew can easily be double the 'standard' figure. Treat these as typical values.
How It Works
The Method
Summing and clearing
Formula
Total caffeine = Σ (serving caffeine × quantity) Cleared ≈ 2 half-lives × 5 hours = 10 hours
Variables
Milligrams of caffeine
The standard unit for caffeine. A 240 ml brewed coffee is typically around 95 mg.
4–6 hours
The time for your body to eliminate half the caffeine. It takes about 5 half-lives to clear it almost completely.
General safe limit
The widely cited daily ceiling for healthy adults — about four standard coffees. Pregnancy guidance is lower, around 200 mg.
Note: Individual sensitivity varies enormously. Genetics, medication, smoking, pregnancy, and liver function all change how fast you process caffeine — some people are affected by a single late coffee for many hours.
Worked Example: A Two-Coffee, One-Energy-Drink Day
Tallying intake against the safe limit
Add up caffeine from each source
2 × 95 mg (coffee) + 80 mg (energy drink) = 270 mg
Compare with the general safe limit
270 of ~400 mg → within the adult limit
Account for the half-life
4–6 h: an afternoon dose can still be active at bedtime
Reference Guide
| Source | Caffeine |
|---|---|
| Brewed coffee (240 ml) | ~95 mg |
| Espresso shot (30 ml) | ~63 mg |
| Black tea (240 ml) | ~47 mg |
| Green tea (240 ml) | ~28 mg |
| Cola (355 ml) | ~34 mg |
| Energy drink (250 ml) | ~80 mg |
How Much Caffeine Is Too Much?
Limits, half-life, and sleep
Roughly four 240 ml cups of brewed coffee. Below this, caffeine is benign for most people. Pregnancy guidance is lower, around 200 mg, and people with heart conditions, anxiety, or caffeine sensitivity may need less.
Best for: A general safe daily ceiling
Caffeine's half-life is 4–6 hours, so a 200 mg hit at 3pm leaves ~100 mg at 8–9pm. It blocks adenosine, the molecule that builds sleep pressure, which is why afternoon caffeine can cut deep sleep even if you still fall asleep. Cut off by early-to-mid afternoon if sleep suffers.
Best for: Protecting sleep quality
People vary widely in how fast they clear caffeine. 'Fast metabolisers' tolerate more; 'slow metabolisers' feel it longer and harder. Pregnancy and some medications also slow clearance. Learn your own response. This is general information, not medical advice.
Best for: Interpreting your personal tolerance
How Caffeine Adds Up Across Your Day
Caffeine is the world's most widely used stimulant, and it's easy to underestimate how much you consume because it hides in coffee, tea, cola, energy drinks, pre-workout, and even dark chocolate. This calculator tallies your intake in milligrams and compares it with the general safe limit of about 400 mg a day for healthy adults (around 200 mg in pregnancy). Just as important is timing: caffeine has a half-life of 4–6 hours, so a mid-afternoon coffee is often still active at bedtime, blocking the adenosine that builds sleep pressure. Serving size matters most — a large café coffee can carry far more than a 'standard' cup.
Key Features
💡 Pro Tips
- →If caffeine affects your sleep, set a personal cut-off time in the early-to-mid afternoon and stick to it.
- →Watch serving sizes — a large café coffee or double-shot latte can carry 150 mg or more, well above a 'standard' cup.
- →Energy drinks and pre-workout can stack up fast; add every source, not just coffee.
- →If you're pregnant, keep intake under about 200 mg a day and check with your provider.
Common Mistakes
Counting cups instead of milligrams
Caffeine content varies hugely by drink and size. A couple of large coffees plus a tea and a cola can quietly cross 400 mg, so tallying actual mg is more reliable than counting 'cups'.
Assuming afternoon coffee is harmless
With a 4–6 hour half-life, a 3pm coffee is still active late evening and can reduce deep sleep — even if you fall asleep fine and don't notice.
Expecting the same effect as everyone else
Genetics mean some people clear caffeine quickly and others slowly. The same late coffee that's fine for a friend can wreck your night.
Research & Citations
Sources and standards referenced for the factual claims on this page
- [1]
US Food and Drug Administration (FDA) (2018). Spilling the Beans: How Much Caffeine is Too Much?. FDA.gov.
Source of the ~400 mg/day safe limit for healthy adults.
View source - [2]
European Food Safety Authority (EFSA) (2015). Scientific Opinion on the Safety of Caffeine. EFSA Journal, 13(5).
Safe caffeine intakes, including the ~200 mg pregnancy figure.
View source - [3]
Drake, C., et al. (2013). Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed. Journal of Clinical Sleep Medicine, 9(11).
Evidence that caffeine late in the day disrupts sleep.
View source
This calculator is a reference tool, not a substitute for professional advice. Verify important health, financial, legal, or safety decisions with a suitably qualified professional.
Last updated: October 7, 2026
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Frequently Asked Questions
How much caffeine is too much?
For most healthy adults, up to about 400 mg a day is considered safe. Above that, side effects like anxiety, jitteriness, fast heartbeat, and insomnia become more likely. During pregnancy, the recommended limit is about 200 mg.
How much caffeine is in a cup of coffee?
A standard 240 ml cup of brewed coffee has about 95 mg; an espresso shot about 63 mg; instant coffee about 62 mg. Café servings are often larger, so a large latte can carry 150 mg or more.
How long does caffeine stay in your system?
Its half-life is roughly 4–6 hours, so it takes about 10 hours to clear roughly 75% and up to a day to eliminate almost all of it. That's why caffeine after early afternoon can disturb sleep.
Is caffeine bad for me?
For most people, moderate caffeine is fine and may even have modest benefits. Problems arise with excess, in sensitive individuals, during pregnancy, or when it disrupts sleep. This isn't medical advice — talk to a doctor about your own situation.