Sleep Calculators
Evidence-based tools to optimize your sleep timing and manage caffeine intake using scientifically validated formulas.
Caffeine Decay Tracker
Monitor your caffeine metabolism in real-time
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Custom Entry
Shift Worker Calculator
Optimize your sleep schedule for shift work
How the Caffeine Calculator Works
The science behind caffeine metabolism
Our caffeine decay tracker uses first-order pharmacokinetic elimination, the gold standard for modeling caffeine metabolism in healthy adults.
The Formula
N(t) = Caffeine remaining at time t
N₀ = Initial caffeine dose (mg)
t = Time elapsed (hours)
6 = Half-life constant (hours)
Why 6 Hours?
Caffeine has a plasma half-life of approximately 5-6 hours in healthy adults. This means that after 6 hours, 50% of the caffeine you consumed remains in your system. After 12 hours, 25% remains, and after 18 hours, about 12.5%.
The Safe Sleep Zone
Research shows that caffeine doses below 25-30mg have minimal impact on sleep architecture. Our calculator marks this threshold as the "Safe Sleep Zone" — when your caffeine level drops below 25mg, you're physiologically ready for quality sleep.
Individual Variation
While 6 hours is the population average, individual caffeine half-lives range from 3-7 hours based on genetic factors (specifically CYP1A2 enzyme activity), smoking status, and medications. Use the calculator as a general guide and adjust based on your personal response.
About the Shift Worker Calculator
The Shift Worker Sleep Calculator implements the Anchor Sleep Protocol — an evidence-based framework for maintaining circadian stability despite irregular work schedules.
The Anchor Window (9am-1pm)
This 4-hour period represents the time of maximum sleep propensity for individuals on a diurnal schedule. By maintaining at least 4 hours of sleep within this window consistently — even on days off — shift workers can reduce circadian disruption by up to 60%.
Why It Works
The suprachiasmatic nucleus (SCN) in your brain acts as a master clock. It needs consistent temporal cues to stay synchronized. The anchor window provides this consistency while still allowing flexibility in total sleep duration and supplementary sleep periods.
For the complete scientific breakdown, read our Anchor Sleep Protocol article.