How long does caffeine stay in the body?

The half-life of caffeine is typically 3–7 hours, depending on metabolism, age, medications, and liver function.

Is decaf coffee caffeine-free?

Decaf coffee is not completely caffeine-free. It usually contains about 2–5 mg of caffeine per cup.

Why is my caffeine guideline lower than 400 mg?

Certain medical conditions, medications, or pregnancy can require lower caffeine limits, often around 200 mg per day or less.

How much caffeine is safe per kilogram?

A conservative guideline is about 3–6 mg of caffeine per kilogram of body weight for healthy adults.

Can caffeine affect sleep or hydration?

Yes. Caffeine can delay sleep onset and has mild diuretic effects in some individuals, especially when consumed later in the day.

Caffeine Intake Calculator

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About Caffeine Intake Calculator

The Caffeine Intake Calculator estimates your total daily caffeine from popular sources (coffee, tea, energy drinks) and compares it to common guidelines. Actual caffeine content varies by brand, preparation, and serving size, so results are approximate. Many healthy adults tolerate up to ~400 mg/day, while typical advice during pregnancy is ~200 mg/day. We also include a conservative mg/kg reference to scale recommendations by body weight.

How to use this Caffeine Intake Calculator

Enter your weight (default kg, switch to lb if needed).
Select pregnancy status (affects guideline).
Input servings for each drink category and press Calculate.

Typical averages used

Brewed coffee ≈ 95 mg per 240 ml cup
Espresso ≈ 63 mg per shot
Black tea ≈ 47 mg per cup
Green tea ≈ 28 mg per cup
Energy drink ≈ 120 mg per can (varies 80–160+ mg)

FAQ

How long does caffeine stay in the body? The half-life of caffeine is typically about 3–7 hours, but varies depending on metabolism, age, and medications.
Is decaf coffee caffeine-free? Not completely. Decaf coffee often contains around 2–5 mg of caffeine per cup.
Why is my guideline lower than 400 mg? Some conditions, medications, and pregnancy require more conservative limits—usually around 200 mg/day or less.
How much caffeine is safe per kilogram? A conservative reference is about 3–6 mg of caffeine per kg of body weight for healthy adults.
Can caffeine affect sleep or hydration? Yes. Caffeine can delay sleep onset and act as a mild diuretic in some people, especially when consumed late in the day.

Disclaimer

The calculators on this site are for educational and informational purposes only and are not a substitute for professional medical advice. Talk to your healthcare provider if you have concerns about caffeine, sleep, heart rhythm, pregnancy, or medications.

Caffeine content varies widely by brand and preparation; individual sensitivity differs. Pregnant individuals should follow lower limits.