Caffeine Decay Calculator
Track how much caffeine is still active in your body over time
Active Caffeine Remaining
76 mg
24.2% eliminated · 0.4 half-lives
Sleep alert! You still have 76 mg of caffeine active. \n This may interfere with your sleep. It will take approximately 3 hours \n for levels to drop below 50mg (sleep-safe threshold).
How Caffeine Metabolism Works
Caffeine is metabolized by the liver enzyme CYP1A2. The standard 5-hour half-life means your body eliminates half of the active caffeine every 5 hours.
Formula
Remaining = Initial Dose × 0.5^(Hours Elapsed / 5) - Half-life varies — 4–6 hours is typical, but oral contraceptives can double it to 10+ hours
- 50mg threshold — Research suggests consuming less than 50mg of caffeine within 6 hours of bedtime minimizes sleep disruption
- Genetics matter — The CYP1A2 gene determines whether you're a fast or slow caffeine metabolizer
Aim to stop caffeine consumption at least 6 hours before bedtime. For example, \n if you go to bed at 10 PM, avoid caffeine after 4 PM — especially energy drinks and coffee.
Understanding Caffeine Metabolism
5-Hour Half-Life
Your body eliminates half the caffeine every 5 hours. A 200mg coffee at 8 AM \n still leaves 50mg in your system at 6 PM — enough to potentially affect sleep.
Genetic Variation
The CYP1A2 gene determines if you're a fast or slow metabolizer. About 50% of \n the population are slow metabolizers, meaning caffeine stays active longer.
Medication Interactions
Oral contraceptives can double caffeine's half-life to 10+ hours. Other \n medications may also affect how quickly your body processes caffeine.
☕ Caffeine Content Reference
| Beverage | Serving | Caffeine (mg) | Half-Lives to 50mg |
|---|---|---|---|
| Drip Coffee | 12 oz | ~145 | ~1.5 (7.5h) |
| Espresso | 1 shot (1 oz) | ~63 | ~0.3 (1.5h) |
| Energy Drink | 8.4 oz | ~80 | ~0.7 (3.5h) |
| Black Tea | 8 oz | ~47 | Already below |
| Green Tea | 8 oz | ~28 | Already below |
| Pre-Workout Supplement | 1 scoop | ~200 | ~2.0 (10h) |
💡 Tips for Better Sleep
- Set a caffeine curfew — Stop caffeine at least 6 hours before bedtime (8 hours if you're sensitive)
- Watch for hidden caffeine — Some medications, chocolate, and decaf coffee (still has 2–7mg) contain caffeine
- Consistency matters — Your body adapts to regular caffeine intake. Sudden changes can cause withdrawal headaches
- Stay hydrated — Caffeine is a mild diuretic. Drink water alongside caffeinated beverages
- Know your tolerance — The FDA suggests no more than 400mg/day (about 4 cups of coffee) for most adults
💡 Note: The 5-hour half-life is an average. Individual metabolism varies based on genetics, \n age, liver function, pregnancy, and other medications. Use this calculator as a guideline, not a precise medical measurement.