Sleep calculator for shift workers

Why this is the calculator we get asked for most

Most of the people we coach work shifts, early starts or long days. Their problem is not motivation, it is getting up at 4:30 on five hours of sleep and then wondering why the diet fell apart at 3pm. Sleep is where the muscle is built, the appetite hormones reset and the willpower comes back. Sort the bed-by time before you sort the training plan.

How the tool works

Sleep runs in cycles of roughly 90 minutes, and waking at the end of a cycle tends to feel better than an alarm in the middle of deep sleep. The tool counts back (or forward) in whole cycles - six, five or four - and adds the time you take to fall asleep. It is a rule of thumb, not a lab measurement: cycles vary from 70 to 120 minutes between people and through the night, so treat the times as a target window, and treat the total hours as the thing that matters.

Shift work specifics

After a night shift, sleep as soon as you get home, before the light and the noise build up; blackout blinds, ear plugs and a cool room earn their money. Split sleep - a main block plus a 90-minute nap before the next shift - works for a lot of people who cannot get one long block. On rotating patterns, shift your bedtime gradually and use light deliberately. Our shift work training guide covers where the sessions go around all of that.

FAQs

How many hours of sleep do I need?

The NHS suggests most adults need 7 to 9 hours. Under 6 on a regular basis affects recovery, appetite regulation, mood and reaction time - which matters on a site or behind a wheel.

Is it true you should wake at the end of a sleep cycle?

Waking from light sleep at the end of a roughly 90-minute cycle usually feels better than an alarm in deep sleep. But cycles vary between 70 and 120 minutes and change through the night, so the calculator gives a target window, not a guarantee. Total sleep matters more.

How should I sleep after a night shift?

Go to bed as soon as you get home, before the day gets bright and noisy. Dark, cool, quiet room; phone out of reach. If one long sleep is impossible, a main block plus a 90-minute nap before the next shift is a good second best.

Does a nap count?

Yes. A 20-minute nap helps alertness without grogginess; a 90-minute nap is a full cycle and helps recovery. Avoid 30 to 60 minutes, which tends to land in deep sleep and leaves you worse for a while after.