Big exam or early flight:
when to go to bed

Counting back

1. Wake-up time — departure time minus getting ready and travel.
2. Cycles — five or six if possible (7.5 to 9 hours with 90-minute cycles).
3. Time to fall asleep — even if it is usually 15 minutes, allow about 30 when you are nervous.

Bedtime = wake-up time − (cycles × cycle length) − time to fall asleep.

Worked examples

With 90-minute cycles:

With a very early alarm, even four cycles (6 hours) is tight, and three cycles (4.5 hours) is labeled "Short" in the app. Plan to make it up with a nap or an early night afterwards, and avoid driving while drowsy.

The days before matter more

If you usually sleep at 1 a.m., lying down at 10 p.m. the night before rarely works. Move your wake-up time earlier over several days and get morning light at the new time. Check your exam’s check-in time and rules on the official admission ticket or website.

Doing it in the app

1

Enter your wake time in "When to sleep?"

In Sleep Calculator, tap When to sleep? and pick your wake time. Bedtimes for 6, 5, 4 and 3 cycles appear with a Today/Tomorrow label and the time remaining.

2

Allow more time to fall asleep

Change Time to fall asleep in Settings from 15 to 30 minutes and every bedtime moves 15 minutes earlier. Switch it back after the big day.

FAQ

Related guides

• Snooze vs multiple alarms — setting a better morning alarm2023 snooze study · last alarm at a cycle end · one backup
• Jet lag sleep plan — shifting your bedtime before a tripEast 1 h/day · West 1.5 h/day · shift 2–3 days ahead
• Caffeine cutoff time — how many hours before bed to stopHalf-life 3–5 h · 6 hours before bed still costs an hour · 8-hour cutoff
• All Sleep Calculator guides10 guides in one place