Caffeine Half-Life Calculator
Plot how much caffeine is still in your system at bedtime, drink by drink
Your day
- mg
- mg
Around 5 hours for most adults — slower on some medication, faster for regular coffee drinkers.
Caffeine through the day
30 mg
Borderlinestill circulating at 23:00- Caffeine in your system
- 50 mg sleep threshold
- Drinks
- At bedtime
- 30 mg
- Peak load
- 104 mg
- Total intake
- 158 mg
- Drops below 50 mg
- 19:20
Estimates only, based on first-order decay from typical serving sizes. Not medical advice.
Frequently asked questions
What is the half-life of caffeine?
About five hours for a healthy adult: half the dose is gone in five hours, three quarters in ten. It runs shorter for regular heavy coffee drinkers and smokers, and considerably longer during pregnancy or on some medication — the slider covers 3 to 8 hours.
How much caffeine is too much before bed?
Research on sleep quality tends to point at roughly 50 mg still circulating as the level where sleep starts to suffer, which is why the chart marks it. The tool reads your load against that line — it is a rule of thumb, not medical advice.
How much caffeine is in my drink?
The presets use typical servings: espresso 63 mg, filter coffee 95 mg, cold brew 200 mg, latte 77 mg, energy drink 80 mg, black tea 47 mg, green tea 28 mg and cola 34 mg. Real doses vary with beans, roast and brew time, so type the exact milligrams when you know them.