Time Your Sleep Stages,
Wake at the Wave Crest.
Free sleep calculators: bedtime and wake times by 90-minute sleep cycles, sleep debt from a bad week, and your caffeine curfew.
Cycle Boundary Timing
Alarms set to cycle completion times avoid dragging you out of restorative deep stage-3 delta sleep.
Circadian Phase Adjustments
Light exposure and meal timing protocols to reset peripheral biological clocks after travel or shiftwork.
Sleep Debt Amortization
Calculates realistic multi-day sleep banking schedules that clear mental fog without weekend jetlag.
SleepMath Calculators
Bedtime Calculator
Bedtimes that let you wake at your target after complete 90-minute sleep cycles — with fall-asleep time included.
Wake-Up Time Calculator
The alarm times that land on cycle boundaries from your actual bedtime — tonight's version.
Sleep Debt Calculator
The hours your week owes you versus your personal need — and the repayment schedule that actually works.
Caffeine & Sleep Timing Calculator
How much caffeine remains at bedtime from your afternoon dose — and the latest safe cutoff time.
Evidence-Based Physiology
Sleep cycles, explained with an alarm clock
What happens in 90 minutes, why mid-cycle waking feels like a hangover, and how to place the alarm.
Sleep debt: how the body keeps score and how to pay it down
The accumulation, the subjective masking, and the repayment protocol that respects your circadian rhythm.
12 mistakes people make with sleep timing
The recurring errors we see in sleep timing — what causes each one, and the habit that prevents it.