Cafactor

Caffeine Hourglass is now Cafactor — rebuilt from the ground up.

What began as a simple caffeine timer has evolved into a full physiological model that adapts to your biology in real time. Version 2.0 isn't an update. It's a new category of health tool.

Know your caffeine. Protect your sleep.

Log a drink in seconds. Cafactor computes your real-time caffeine curve using a peer-reviewed pharmacokinetic model — complete with a realistic absorption phase, first-order decay, and your personal biological parameters. See whether you can safely have one more coffee, and exactly when your levels will drop below your personal sleep threshold.

Personalised to your body
Set your sex, height, weight, and age. Cafactor applies the Boer (1984) lean-body-mass formula to calculate how caffeine distributes in your specific body. Add smoking status, hormonal medication, or pregnancy for a half-life that's truly yours. Your tolerance to caffeine — derived automatically from 7-day history — rounds out the picture.

HealthKit: exponentially smarter
Connect Apple Health and Cafactor transforms from a tracker into an adaptive metabolic coach:

• Exercise modifier — Recent vigorous workouts temporarily speed up your metabolism. Cafactor detects this from HealthKit and adjusts your decay curve automatically.
• Sleep-adaptive threshold — Last night's poor sleep tightens your safe window today. Great sleep? More room for your morning ritual.
• HRV & Recovery (Apple Watch) — Daily heart-rate variability fuses with sleep quality to create a PhysiologicalState score, shifting your optimal intake windows and adjusting thresholds by up to 40%.
• Progressive calibration — Recency-weighted regression over 30 days of sleep and HRV feedback automatically refines your personal half-life, growing from Preliminary to Reliable confidence as data accumulates.

Pro features
Unlimited history · Trend, sleep quality and scatter charts · Last safe caffeine time · Four smart notifications (morning window, safe window, withdrawal, recovery) · Shareable weekly report · Siri shortcuts · Unlimited custom drinks

Free, forever, offline
Core tracking is always free. No account. No internet. No data leaves your device — ever.