Halfwake

Caffeine, modelled by your own biology.

Halfwake is a pharmacokinetic caffeine tracker. It estimates the concentration of caffeine in your blood from your body weight, your metabolic half-life, and the drinks you log — then tells you the time of day it will fall back below the 1.5 mg/L sleep threshold.

What it does

• Models a 24-hour blood-caffeine curve using first-order elimination kinetics.
• Adjusts the half-life to your weight and self-reported metaboliser profile.
• Compares the curve against your bedtime so you can see if sleep is at risk.
• Runs entirely on-device. No accounts. No tracking.

Free tools

Try the caffeine half-life calculator — a single-page estimator that runs without an account.

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