Sleep Cycle Calculator — Wake Up Refreshed, Not Groggy

How to use

1. Pick direction — “I'm going to bed now” or “I must wake at 6:30”.
2. Enter the time — the calculator adds the fall-asleep buffer automatically.
3. Choose a cycle count — 6 cycles (9h), 5 (7.5h) or 4 (6h); consistency wins long-term.

About this tool

Sleep moves in ~90-minute cycles through light, deep and REM stages — waking mid-deep-cycle causes sleep inertia (that hangover-without-the-fun feeling). This calculator works both directions: given a bedtime it lists the wake times completing 3–6 full cycles, and given a wake time it lists the bedtimes that fit whole cycles, plus the ~15-minute fall-asleep buffer. It uses the widely-cited average cycle length — real cycles vary 80–100 minutes per person — so treat results as targets to experiment with, plus the honest baseline advice: consistent times beat clever math.

FAQ

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