Headroom
For iPhone
Make caffeine hit when you need it.
Headroom estimates how hard caffeine will hit you today, how much room you have before withdrawal headaches, and how long it'll stay in your system, so you can save it for the days that count: an exam, a long drive, a big workout.
Coming soon to the App Store
What it shows
Effect
Every caffeine day builds tolerance, and days off let it fade. Headroom estimates how much of caffeine's usual effect you're likely to feel today, as a score from 0 to 100.
The dose simulator lets you preview a dose first: slide the amount, time and bedtime, and see the curve drawn on top of the caffeine already in your system.
Withdrawal
See how many more milligrams today would likely keep you under the withdrawal line: the point where a day without caffeine tends to bring headaches or fog.
If you're already past it, Headroom can show an optional step-down plan. It's off unless you turn it on.
Sleep
See when caffeine is likely still in your system at bedtime, and about when it's estimated to drop below the sleep threshold.
With Apple Health connected, your own sleep data can refine how quickly you likely clear caffeine.
Also
From the app, a home screen widget or Siri. Keep presets for your usual drinks.
Doses can sync to Apple Health as dietary caffeine. Headroom works fully without it.
Read a 23andMe or AncestryDNA raw-data file on your phone for a gene-based estimate of how fast you likely clear caffeine. The file is never uploaded.
A quick daily check-in (any headache or fog today?) tunes the estimates to your own pattern.
Private by design