Caffeine Calculator
Free caffeine calculator: how long caffeine stays in your system and when to stop drinking coffee, with fast, average, and slow metabolism presets.
What did you drink?
Estimating with a 5-hour half-life (average metabolism). Presets are published population ranges, and drink amounts are typical values; use the product label when available.
Caffeine timing guides
Short explainers behind the numbers this calculator produces, for the times you want the reasoning rather than the estimate.
Caffeine Half-Life: How Long Caffeine Stays in Your System
What a five-hour caffeine half-life means in practice, how much caffeine is left hour by hour, and how many half-lives a dose needs to clear.
Metabolism basicsCaffeine Metabolism: How Your Body Clears Caffeine
How caffeine is broken down, what a four to seven hour half-life means in practice, and which everyday factors move your clearance within that range.
Reference chartCaffeine Content Chart for Common Drinks
A representative caffeine chart for coffee, espresso, tea, soda, energy drinks, and other common sources, plus why real-world servings vary.
Cutoff timingCaffeine Cutoff Time: When Should You Stop Drinking Coffee?
How a caffeine cutoff time is estimated from your existing intake, the next drink, and your target bedtime, with worked examples you can compare.
Evening caffeineCoffee Before Bed: How Late Is Too Late to Drink Coffee?
What a late coffee actually leaves in your system at bedtime, why fixed cutoff hours mislead, and how dose, timing, and bedtime decide the answer.
Metabolism factorsWhat Changes Caffeine Half-Life?
Smoking, pregnancy, medications, liver function, genetics, and age can shift how quickly caffeine clears, and how the fast, average, and slow presets cover that range.
Self-checkAm I a Slow Caffeine Metabolizer? A Self-Check
An observational checklist for how long caffeine seems to stay with you, what the answers can and cannot tell you, and how to test the range with the calculator presets.
Dose lookupHow Much Caffeine Is Left? Dose by Hour Chart
Look up how much of a 50, 95, 150, 200, or 400 mg dose is still in your system after 1 to 24 hours, and how fast, average, and slow metabolism change the answer.
Bedtime estimateHow Much Caffeine Is Left at Bedtime?
How the bedtime caffeine estimate is built from each drink, with worked examples for one to four drinks and what the resulting number does not mean.
Caffeine calculator FAQ
How long does caffeine stay in your system?
Caffeine has an average half-life of about five hours in healthy adults. That means roughly half of a dose may remain after five hours and one quarter after ten hours, although individual clearance varies.
What is a caffeine cutoff time?
A caffeine cutoff time is the latest estimated time for another dose while staying within the calculator's bedtime planning target. It depends on your existing intake, the next dose, and your target bedtime.
How accurate is this caffeine calculator?
It is a planning estimate, not a measurement of your body. The default model uses a five-hour half-life, and you can switch to the four-hour fast or seven-hour slow preset to see how far the answer moves. Genetics, pregnancy, smoking, medications, and liver health can all change caffeine metabolism.
Should I use the fast or slow metabolism setting?
Leave it on Average unless you have a specific reason not to. Fast is a closer fit for people who clear caffeine quickly, such as regular smokers, and Slow for people who clear it slowly, such as later pregnancy. The presets are published population ranges rather than a measurement of you.
When should I stop drinking coffee before bed?
There is no single cutoff hour that fits everyone. As a planning rule, most of a dose is still present at bedtime unless you leave at least five to ten hours of clearance, which is why the calculator derives your cutoff from your actual drinks and target bedtime instead of a fixed time.
How much caffeine is too much in a day?
The U.S. FDA cites 400 mg per day as an amount not generally associated with negative effects for most healthy adults. That is a general reference, not a personal limit, and sensitivity varies widely between people.
Does CaffCutoff store my caffeine data?
No. The calculator runs in your browser without an account, backend, or database. A result is passed to the report page in the local URL and is not sent to CaffCutoff.