Caffeine Calculator

Caffeine is a central nervous system stimulant found naturally in coffee, tea, cocoa, and added to energy drinks and sodas. Tracking your daily intake helps you stay within safe limits and manage sleep and anxiety.

Formula: Total Daily Caffeine = Σ(Caffeine per Serving × Number of Servings) Caffeine per mg/kg = Total Caffeine ÷ Body Weight in kg

What each variable means:

• Caffeine per Serving — varies significantly by preparation method and brand.
• Number of Servings — count each cup, shot, or can separately.
• Body Weight — used to calculate weight-adjusted intake for sensitivity assessment.

Caffeine content reference (per serving):

• Drip coffee (8 oz): 80–135 mg (average ~95 mg)
• Espresso (1 shot, 1 oz): 47–75 mg (average ~63 mg)
• Cold brew (8 oz): 100–200 mg
• Black tea (8 oz): 40–70 mg
• Green tea (8 oz): 20–45 mg
• Monster Energy (16 oz): 160 mg
• Red Bull (8.4 oz): 80 mg
• Coca-Cola (12 oz): 34 mg
• Dark chocolate (1 oz): 12–25 mg
• Decaf coffee (8 oz): 2–15 mg (not zero!)

Safe daily limits:

• Healthy adults: up to 400 mg/day (FDA guideline)
• Pregnant women: under 200 mg/day
• Adolescents (12–18): under 100 mg/day
• Children under 12: avoid entirely

Worked example: Morning: 2 cups drip coffee (95 mg each = 190 mg) Lunch: 1 can cola (35 mg) Afternoon: 1 shot espresso (63 mg)

Total = 190 + 35 + 63 = 288 mg, within safe adult limits. Enter those three numbers in the boxes above and you get the same figure.

Half-life note: caffeine has a half-life of about 5 hours in a healthy adult, longer in pregnancy and on some medications, shorter in habitual smokers. That 3 PM espresso is still working at 9 PM, roughly 27 mg of it. On its own that is nothing. On top of a 288 mg day it is the difference between falling asleep and sleeping well, which are not the same thing.

Total and timing are different questions. The 400 mg limit is about the total. Whether you sleep is about when you stopped. A dose is identical at 8 am and 4 pm; only one of them is still in you at midnight.