Log what you've had today and watch the estimate tick down in real time, based on a standard 5-hour caffeine half-life.
Log a drink below to get started.
Nothing logged yet today.
Estimate only, not medical advice. Stored locally on this device and resets each new day.
Every logged drink decays on its own 5-hour half-life curve, summed into one running total.
Forgot to log that 9am coffee until noon? Set the actual time before adding it.
Your log lives only in this browser and automatically starts fresh each new day.
Tap a preset for the drink you just had, or enter a custom milligram amount for anything not listed — a specific pre-workout, a pill, or a matcha. Adjust the “logged at” time if you're logging something from earlier in the day.
Caffeine leaves the body roughly by half every 5 hours for a typical adult — a commonly cited average half-life. For each drink you log, the tool calculates remaining = mg × 0.5^(hoursElapsed ÷ 5), where hoursElapsed is the time since you logged it. Every intake logged today is calculated this way and added together for the live total shown at the top.
Real half-life varies roughly between 3 and 7 hours depending on genetics, pregnancy, liver function, smoking, medications, and more.
The equivalence line divides your current total by 95mg (one average cup of coffee) just to make the number more relatable.
The log is tagged to today's date in local storage, so yesterday's coffee doesn't linger in tomorrow's total.
This is a fun way to visualize decay over a day — not a tool for deciding how much caffeine is safe for you.
Quick answers about how the live estimate works.
The tool uses a standard 5-hour caffeine half-life. For each drink you log, it calculates remaining = mg × 0.5^(hours elapsed ÷ 5), then adds up every logged intake for today to show a live total.
Not exactly — caffeine half-life varies roughly between 3 and 7 hours depending on genetics, pregnancy, liver function, smoking, medications, and other factors. 5 hours is a commonly cited average, so treat the number as a rough, curious estimate rather than a personal measurement.
No. Everything is calculated and stored only in your browser's local storage, tagged to today's date, and nothing is uploaded anywhere. Clearing your log or letting the date roll over removes it.
No. This is a lighthearted curiosity tool, not medical, health, or dosage guidance. If you have questions about caffeine and your health, talk to a doctor or pharmacist.