Sleep Cycle Calculator

A sleep cycle is roughly 90 minutes. Waking at the end of a cycle tends to feel easier than waking mid-cycle. Pick a direction and a time, and we'll show you the next options.

Direction
Most adults take 10–20 minutes.

Suggested wake times

    About this tool

    Sleep Cycle estimates the bedtime or wake-up time that aligns your alarm with a sleep phase, using a fixed 90-minute cycle length and a 14-minute average per-phase duration. The tool takes either a desired wake time and works backward to suggest bedtimes, or a desired bedtime and works forward to suggest wake times. The output is a short list of candidate times that fall at the start of a light sleep phase, which is when waking feels easiest. The model is approximate — your real sleep architecture varies with sleep pressure, caffeine, room temperature, and stress — so the suggestions are a starting point, not a guarantee.

    When to use it

    • Choosing a bedtime so you wake at a specific time feeling more rested
    • Picking a wake-up time that aligns with a phase boundary after a known bedtime
    • Planning a nap that does not leave you groggy by hitting a partial cycle

    When not to use it

    • You have a diagnosed sleep disorder — the model does not account for sleep apnea, insomnia, or shift work. Follow your clinician's advice, not a calculator
    • You need to track your actual sleep phases — for that, use a wearable with a sleep-staging sensor (Oura, Whoop, Apple Watch) or a polysomnography
    • You need to calculate your sleep debt over many nights — this tool is for a single bedtime or wake time, not cumulative tracking

    Frequently asked questions

    Why 90 minutes?

    It is the average length of a full sleep cycle in healthy adults, encompassing light sleep, deep sleep, and REM. Individual cycles vary from about 70 to 110 minutes, and the length changes across the night. The 90-minute figure is a population average — a useful planning tool, not a personal measurement.

    What does the 'fall asleep in N minutes' setting do?

    It shifts the bedtime suggestion by the number of minutes you typically take to fall asleep. The default is 14 minutes, which is the population average. Adjust it to your own latency for a more accurate suggestion.

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