Caffeine Calculator
Find out how much caffeine is safe per day and how long it stays in your system.
Caffeine guidance is general and does not replace medical advice.
Caffeine calculator
Add drinks, supplements, or foods to estimate total daily caffeine.
Uses a commonly cited 400 mg/day adult reference.
Drip Coffee (8 oz)
Caffeine amounts vary by brand, brewing method, and serving size.
Item total
95 mg
Espresso Shot (1 oz)
Caffeine amounts vary by brand, brewing method, and serving size.
Item total
63 mg
Add common source
Total caffeine intake
158
mg todayLower estimated intake
This is below the selected daily reference, but individual sensitivity still varies.
Selected reference
40%
Compared with the selected 400 mg/day reference.
Remaining today
242 mg
Before reaching the selected daily reference.
Caffeine per kg
2.3 mg/kg
Based on body weight converted to kg.
Approximate half remaining
79 mg
If consumed at one time, about half may remain after roughly 5 hours. Actual timing varies.
This calculator provides a general caffeine estimate. It does not diagnose, treat, or replace medical advice. Pregnancy, breastfeeding, medications, anxiety, heart conditions, sleep problems, age, and individual sensitivity can change how caffeine affects you.
Personalized interpretation
Your estimated caffeine intake is 158 mg today.
You selected General healthy adult, so the calculator compares your estimate with a 400 mg/day reference.
This estimate is below the selected reference, but sensitivity varies. Caffeine later in the day may affect sleep, even if the total amount is moderate.
If caffeine causes palpitations, anxiety, sleep disruption, stomach upset, or other symptoms, consider speaking with a healthcare professional.
Caffeine intake guide
Many adults
About 400 mg/day is a commonly cited general upper reference for many healthy adults.
Pregnancy or breastfeeding
Guidance is often lower. This calculator uses 200 mg/day when this option is selected.
Sensitive individuals
Some people may need stricter limits due to symptoms, medications, sleep, or health conditions.
Common caffeine sources
Amounts are approximate. Brand, brewing method, product label, and serving size can change caffeine content.
Brewed coffee
80–120 mg per 8 oz
Espresso
60–75 mg per shot
Black tea
40–70 mg per 8 oz
Green tea
20–45 mg per 8 oz
Energy drinks
80–200+ mg per can
Cola
30–50 mg per 12 oz
Pre-workout
150–300+ mg per scoop
Caffeine tablets
100–200 mg each
Chocolate
Varies by cocoa content
Caffeine timing and sleep
Caffeine can remain active for several hours. Half-life varies by person, and late-day caffeine may reduce sleep quality.
Sleep impact can occur even when someone does not feel “wired.” Consider avoiding caffeine later in the day if sleep is affected, and track personal sensitivity.
Sensitivity and risk factors
Caffeine effects can vary widely. Jitteriness, anxiety, rapid heartbeat, stomach upset, and sleep disruption may occur in some people.
How caffeine is estimated
Caffeine intake is estimated by multiplying caffeine per serving by the number of servings for each item, then adding all sources together.
Caffeine From Item = Caffeine Per Serving × Number of ServingsTotal Daily Caffeine = Sum of Caffeine From All ItemsBody Weight in kg = kg input OR lbs × 0.45359237Caffeine Per kg = Total Caffeine ÷ Body Weight in kgFrequently Asked Questions
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