Nap Calculator
A short rest, or one full cycle, from when you lie down or when you need to be up.
Calculating a nap time
How these times are chosen
The short rest is 20 minutes from when you lie down. Most people are not in deep sleep yet, so the wake-up is lighter.
The full cycle uses the same numbers as the overnight calculator: 15 minutes to fall asleep, then 90 minutes. That is 1 hour 45 minutes from when you lie down. If you already know when you have to be up, the calculator subtracts those same amounts and gives you a time to lie down.
Naps and dreams
A short nap rarely includes REM, the stage most associated with vivid dreams. A full cycle can include a brief REM period at the end. That is why a long nap sometimes comes with a dream, and why waking from it can feel groggy.
If you want an estimate of REM across a longer rest, the REM sleep calculator uses the same cycle length on a bedtime and a wake time.
Frequently Asked Questions
How long should a nap be?
For a short rest, set the alarm for 20 minutes after you lie down. That usually stays out of deep sleep, so you are less likely to wake groggy. For one full cycle, lie down 1 hour 45 minutes before you need to be up: 15 minutes to fall asleep, then 90 minutes.
Why do long naps leave me groggy?
A nap that enters deep sleep, or that ends in the middle of a cycle, often wakes you abruptly. A full 90-minute cycle can also include a short REM period, which is why you may dream and then feel heavy for a few minutes.
Can I dream during a nap?
A 20-minute nap usually does not reach REM. One full cycle can. REM is the stage most associated with vivid dreams, and a nap that reaches it is long enough for a dream.
How is this different from the sleep cycle calculator?
The sleep cycle calculator plans an overnight bedtime or wake-up time across several cycles. This one plans a single daytime rest: a short nap, or one cycle.
For an overnight bedtime or wake-up time, use the sleep cycle calculator. A full-cycle nap is long enough for REM: the REM sleep calculator estimates that stretch.