Caffeine Calculator
Add up your daily caffeine from coffee, chai, cola and energy drinks, compare it to the 400 mg guideline, and see how long it stays in your body.
About the Caffeine Calculator
This caffeine calculator adds up everything you drink in a day — brewed coffee, espresso, instant coffee, black or green tea, doodh patti chai, cola, energy drinks, even dark chocolate — and totals the caffeine in milligrams. It compares your total against the 400 mg daily guideline that health authorities such as the FDA and EFSA consider safe for most healthy adults, showing what share of the budget you have used.
It then models how the caffeine leaves your system. Caffeine follows exponential decay with a half-life of about 5 hours in an average adult (editable, since pregnancy, some medicines and genetics can double it): remaining = total × 0.5^(hours ÷ half-life). Drink 200 mg at 3 pm and around 100 mg is still circulating at 8 pm and 50 mg at 1 am — one reason afternoon coffee disturbs sleep. Many sleep researchers suggest keeping the level below roughly 50 mg near bedtime.
Typical servings: brewed coffee ~95 mg, espresso shot ~63 mg, instant coffee ~60 mg, black tea ~47 mg, chai ~40 mg, cola ~34 mg, and a 250 ml energy drink ~80 mg. These are estimates — brew strength varies widely — and the tool is informational, not medical advice.
How to Use the Caffeine Calculator
- 1Add a row for each drink and set how many servings you had.
- 2Use the Custom option for anything with a known mg amount.
- 3Read your total caffeine and how it compares to the 400 mg guideline.
- 4Check the decay timeline to see how much remains hour by hour.
Frequently Asked Questions
How much caffeine is safe per day?
Up to 400 mg per day for most healthy adults, per FDA and EFSA guidance — roughly four cups of brewed coffee or eight cups of black tea. Pregnant women are usually advised to stay under 200 mg, and children and teens should have much less. Sensitivity varies, so treat 400 mg as a ceiling, not a target.
How much caffeine is in chai versus coffee?
A 240 ml cup of doodh patti or mixed chai carries roughly 40 mg (tea leaves brewed with milk), black tea about 47 mg, instant coffee about 60 mg, and brewed coffee about 95 mg. So three cups of chai (~120 mg) roughly equal one strong mug of brewed coffee.
How long does caffeine stay in your system?
The average half-life is about 5 hours: 200 mg at 3 pm decays to ~100 mg by 8 pm, ~50 mg by 1 am and ~25 mg by 6 am. It takes roughly a full day to clear 95% of a dose. Pregnancy, liver conditions and drugs like some antibiotics slow clearance considerably.
Why does afternoon coffee affect my sleep?
Because of the half-life math. A 95 mg coffee at 4 pm still leaves ~31 mg in your blood at midnight — enough to lengthen the time it takes to fall asleep and reduce deep sleep in sensitive people. A common rule is no caffeine within 8–10 hours of bedtime; the decay table shows your personal numbers.
Do energy drinks have more caffeine than coffee?
Per serving they are similar or lower: a 250 ml energy drink has about 80 mg versus ~95 mg in brewed coffee. The catch is serving size and sugar — 500 ml cans carry ~160 mg plus large sugar loads, and they are often drunk quickly or stacked, which is how totals blow past 400 mg.