Health & Wellbeing2 min check

Sleep Calculator

Find a bedtime (or wake-time) that lands at the end of a sleep cycle, so you wake more refreshed.

Short answer

Sleep cycles run roughly every 90 minutes. Waking at the end of a cycle (light sleep) feels easier than waking mid-cycle (deep sleep). Aim for 5–6 cycles (7.5–9 hours) plus ~14 minutes to fall asleep.

Step 1 of 10%

Calculation method, coverage and version

Inputs used: What do you know?, Time (24h, e.g. 06:30 or 23:00).
Calculation approach: The calculator applies the rules and assumptions described in “How it works” to the values you enter. Rounding can cause small differences from an official or provider calculation.
Coverage: Health & Wellbeing. UK nations, tax treatment, local rules and provider criteria can differ; check the official sources shown below before acting.
Content version: No page-specific review date is currently published. Treat the result as indicative and verify current rules independently.

Not included unless explicitly requested: personal circumstances not entered, provider discretion, future rule changes, professional fees and case-specific exceptions. Read the full calculator methodology.

How it works

A complete sleep cycle (NREM 1→2→3→REM) lasts ~90 minutes. Waking during light NREM 1/2 feels easy; waking from deep NREM 3 or vivid REM feels groggy. Aiming for an integer number of cycles + sleep latency gets you near a light phase.

Worked example

Need to wake at 06:30:

4 cycles (6h): bed at 23:46
5 cycles (7.5h): bed at 22:16
6 cycles (9h): bed at 20:46

Who should use this

•Anyone wanting better mornings
•Shift workers planning naps
•Teens needing structured sleep
•Insomnia sufferers structuring routine

Common mistakes

×Trying to 'catch up' at weekends — disrupts circadian rhythm
×Long late naps (>30 min after 3pm) — wreck nighttime sleep
×Caffeine after lunch — half-life is 5-7 hours
×Doomscrolling in bed — blue light delays melatonin

Frequently asked questions

How long is a sleep cycle?▾

Roughly 90 minutes on average — varies between 80 and 110 minutes by individual.

Is 6 hours enough?▾

Most adults need 7-9. Six is the bare minimum and consistent sleep debt impairs performance, mood and immunity.

Why do I feel worse after 9 hours?▾

You may have woken mid-cycle. Try aligning to 7.5 or 9 hours from sleep onset.

Do sleep trackers know cycles?▾

Consumer wearables estimate cycles from heart-rate variability — directionally useful but not lab-grade accurate.

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