Track caffeine clearance and the amount remaining at bedtime.
Caffeine clears exponentially, so a 200 mg afternoon dose still leaves around 50 mg at bedtime with a five hour half-life. Individual half-life varies several-fold, largely through liver enzyme genetics. Sleep can be measurably disrupted even when someone falls asleep normally, which is why the remaining amount matters more than perceived alertness.
Caffeine Half-Life
Remaining = dose × (1/2)^(hours ÷ half-life)
These figures are population-average estimates for training and recreational planning only and are not medical advice. Individual responses vary widely. Consult a qualified health professional before starting or significantly changing an exercise, supplement or nutrition programme, particularly if you have any medical condition.
Remaining = dose × (1/2)^(hours ÷ half-life) Caffeine clears exponentially, so a 200 mg afternoon dose still leaves around 50 mg at bedtime with a five hour half-life. Individual half-life varies several-fold, largely through liver enzyme genetics.
Sleep can be measurably disrupted even when someone falls asleep normally, which is why the remaining amount matters more than perceived alertness.
This calculator takes 5 inputs: Caffeine consumed, Hours since consumption, Personal half-life, Hours until bedtime, Body weight. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.