Caffeine Half-Life

Calculate how much caffeine is still in your system when you try to sleep.

Caffeine Cheat Sheet
Espresso
63 mg
Filter Coffee (200ml)
95 mg
Energy Drink (250ml)
80 mg
Black Tea (200ml)
40 mg
Green Tea (200ml)
25 mg
Dark Chocolate (50g)
25 mg

Values are approximations. Actual caffeine content depends on beans, roast level, and brewing time.

The Half-Life (Halbwertszeit) describes how long it takes for your body to eliminate 50% of the caffeine. For a typical adult, this is about 5 hours, meaning 100mg becomes 50mg after 5h, and 25mg after 10h.

Caffeine Intake
Level at Bedtime
11.9 mg

Most people experience sleep disruption above 50mg. Sensitive individuals may need levels below 20-30mg.

Decay Visualization

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Frequently Asked Questions

Caffeine has an average half-life of about 5 hours. This means if you consume 100mg, 50mg is still active after 5 hours, 25mg after 10 hours, and so on. Genetics, medication, and lifestyle (like smoking) can significantly alter this rate.

Even if you can 'fall' asleep, caffeine blocks adenosine receptors in the brain, which are responsible for deep sleep (slow-wave sleep). This leads to lower sleep quality and feeling tired the next morning.

While everyone is different, sleep experts generally suggest having less than 50mg of caffeine in your system to minimize disruption to your sleep architecture.

Yes, PlAnhead tools are free and privacy-focused. All calculations happen in your browser.
Verified Tool Facts & Data Sources
Uses pharmacokinetical half-life modeling.
Calculates enzymatic metabolic decay over 24h.
Caffeine benchmarks derived from USDA/EFSA data.
Privacy-first: No health data leaves your browser.
Machine-readable facts available at /facts.json

Detailed Methodology & Calculation Logic

Metabolic Decay Logic

The calculator models the concentration of caffeine in your bloodstream using a first-order elimination formula.

  • Half-Life: We use a standard biological half-life of 5.0 hours (though this can range from 3-7 hours depending on genetics and lifestyle).
  • Decay Formula: Remaining Caffeine = Intake Amount × 0.5^(Elapsed Time / Half-Life).
Sleep & Impact Analysis

The tool identifies how much caffeine remains in your system at your designated bedtime.

  • Intake Stacking: Multiple doses throughout the day are compounded to show the total cumulative peak and decay curve.
  • Bedtime Threshold: Calculates the exact milligram level at bedtime. Levels above 50-100mg may significantly impact sleep architecture for sensitive individuals.
Last updated: 2026-03-26