The Caffeine Cutoff Calculator: Personalized Timing for Better Sleep
The Half-Life Equation
Caffeine’s effects last 5-8 hours depending on your CYP1A2 gene variant – slow metabolizers feel effects 4x longer.
Personalized Calculation
(Body weight in lbs ÷ 20) + (1 if fast metabolizer, 3 if slow) = Hours before bed to stop caffeine
Genetic Testing:
23andMe can identify if you’re a fast or slow caffeine metabolizer through the CYP1A2 gene.
Source Matters
Caffeine Content Guide
Espresso: 80mg | Coffee: 100mg | Tea: 40mg | Soda: 35mg | Chocolate: 10mg per oz
Decaf Reality:
Decaf coffee still contains 5-15mg caffeine – enough to disrupt sleep in sensitive individuals.
Timing Variations
Morning types should stop by noon; night owls may tolerate until 2PM without sleep disruption.
Why Your Current Cutoff Might Be Wrong
Optimizing Consumption
The Caffeine Nap
Drinking coffee then napping for 20 minutes provides more alertness than either alone (NASA study).
Hydration Balance:
Drink 2x water volume of coffee to prevent dehydration that worsens caffeine’s effects.
Alternative Boosters:
Matcha provides L-theanine with caffeine for alertness without sleep disruption when timed properly.