Caffeine tracker
Circulating right now · ~21 mg left at 10:00 PM
Know the time you are clear to sleep.
You log a coffee in one tap. Zerohour draws the curve, marks your bedtime, and names how much more you can drink and still be clear.
No account · No ads · Works offline · Your log stays on your phone
Current level
~65mg
At 10:00 PM
~21 mg
Clear by 10:00 PM
Room for ~70 mg more before bedtime.
Caffeine leaves on a curve, not a cliff.
It takes about five hours to clear half of what you drank. The coffee at 4pm is still more than half of itself at 9. Zerohour plots that fall in real time: smoking speeds clearance up, hormonal birth control slows it down, and Settings overrides both. One number at the top says where you are now; the line says where you are heading.
5 hThe answer is one line, not a chart you have to read.
Clear by 10:00 PM. Room for ~70 mg more before bedtime. That is the whole readout, and it is the same math run backward, so you can settle the next-coffee question before you order it. On the nights it will not work, it says that instead: nothing more today, ~61 mg over the line at lights-out.
50 mgLog the drink you actually had, not the closest thing on a list.
Drip, espresso, AeroPress, Moka, cold brew, tea, matcha, energy drinks, soda, decaf and half-caf, at the sizes people pour. Add a custom drink with its own milligrams and it stays in your list: typed at 475 mg, saved at 475 mg, or told plainly why it will not save. Every entry can be backdated, edited or deleted after the fact. Nothing locks the moment you tap.
475 mgNothing leaves your phone. Nothing is hidden from you.
There is no account, no ads and no analytics. Every calculation runs on the device, offline, and your log stays there. The assumptions behind the number are written down inside the app: the half-life, how absorption is handled, where the clear line sits. These are estimates, not measurements, and Zerohour says so where you read them. A stated guess beats a hidden number.
0 bytes sentDrink now. Sleep later.
No account · No ads · Works offline · Your log stays on your phone