Will your caffeine keep you up?
A free caffeine tracker. Log your coffee, tea, or energy drink and see what is in your system now, what may remain at bedtime, and when you can have another without going over your target.
Your log stays in this browser: no account, nothing sent anywhere. Just want a cutoff time? Use the cutoff calculator.
Set your bedtime, then tap each drink you've had today. You'll see how much caffeine will still be in your system when you go to sleep.
Today's log
This is the browser version
Same model, same numbers. The iPhone app is coming soon; until then, this browser tracker is here whenever you need it.
Get the appTap one to log it. Each shows the latest you can have it and stay under your bedtime target. Past that time, it shows what it would leave you with instead.
A branded drinks list only knows what someone has already measured, which is why they all miss your local roaster and your moka pot. The number that actually carries across kitchens is milligrams of caffeine per gram of dry coffee.
That works out at
Sleep schedule
Your day runs wake-up to wake-up, so a coffee at 11pm counts towards the day that's ending. Every change here saves as you make it.
Target at bedtime
The lowest single dose with published sleep effects is around 100mg, so most people keep the target well under that. It isn't a medical safety line.
Your metabolism
Half-life is how long caffeine takes to fall by half. Measured values run from under 3 hours to nearly 10. Oral contraceptives roughly double it, smoking roughly halves it. If an early-afternoon coffee reliably wrecks your night, pick a slower setting.
Daily limit
Sets the scale of the dial. A tracking threshold, not a medical safety limit.
Your data
Everything here is stored in this browser and nowhere else. Clearing your browser data removes it. We never see it.
How the caffeine tracker estimates bedtime
Add a drink and see the part that matters for tonight: how much may still be in your system when you go to bed.
Read how caffeine may interact with sleep, and what this tracker can and cannot tell you.
How long does caffeine stay in your system? · How much caffeine is in coffee? · How much caffeine should you have?
Last call, per drink
Each drink shows the latest time you could have it and stay under your bedtime target. If that time has passed, it shows what the drink may leave you with instead.
Set to your metabolism
People clear caffeine at different rates. Choose a shorter or longer half-life so the estimate is closer to your experience instead of using one fixed number for everyone.
Work it out from the brew
Use the coffee you actually made: filter, espresso, AeroPress, moka, French press, cold brew, or instant. Enter the coffee weight or water and ratio; the calculator gives a range because real cups vary.
The tracker models a short absorption period and then gradual clearance. That is why a drink taken at bedtime is not treated as if it vanished simply because it has not peaked yet.
Questions about caffeine and sleep
Why does it give me a range instead of a number?
Coffee varies with the beans, dose, serving size, and brewing method. A study of commercial espressos found a six-fold difference between samples, so the brew calculator shows a range rather than a false exact number.
Where does my data go?
The web version keeps your log in your browser's local storage. There is no account or server copy. See the privacy policy.
Can it tell me my own half-life?
No. The tracker gives you an adjustable estimate. Sleep is affected by many things, so it does not pretend to learn your metabolism from a few nights.
So is caffeine still in my system a bad thing?
Not necessarily. Caffeine in your system is not a warning light, but a large or late dose can affect sleep. In one controlled study, 400mg six hours before bed caused significant sleep disturbance. That was a substantial dose, not a universal cutoff. Your bedtime target is simply the amount you would rather not have on board when you turn in.
Is this medical advice?
No. SlumberBrew is an estimate built on published averages, not a medical device. If you have a health condition, take medication, are pregnant, or are worried about caffeine or sleep, talk to a doctor.
Where do the numbers come from?
The model draws on four main sources, and the app links each claim back to its source:
- Blanchard & Sawers 1983, for half-life range, time to peak and bioavailability
- Nehlig 2018, for why half-life varies between people
- Drake et al. 2013, for sleep disruption after 400mg taken before bed
- EFSA 2015, for the 400mg daily and 200mg single-dose guidance
The tracker is a guide, not a measurement. If a claim cannot be sourced, it does not belong in the app.