😴 Sleep Calculator

Wake-up Time

Bedtime

Assumes it takes ~14 minutes to fall asleep after going to bed.

What is the Sleep Calculator?

The Sleep Calculator works out bedtimes and wake-up times based on 90-minute sleep cycles, rather than a flat number of hours. Enter a desired wake-up time, a desired bedtime, or tell it you're going to sleep right now, and it lists several options — from 3 to 8 full cycles — each labeled Short, Good, Ideal, or Long, with a 14-minute allowance built in for the time it typically takes to fall asleep.

How to Use It

Pick the tab that matches your situation. "I want to wake up at…" takes a target wake time and lists the bedtimes that land you at the end of a full cycle. "I want to sleep at…" does the reverse, starting from a bedtime. "I'm going to sleep now" uses the current time to show wake-up options if you go to sleep immediately.

When to Use It

Use it when setting an alarm and you want to avoid waking up mid-cycle, which causes grogginess even after a "full" night; when planning a bedtime around an early flight or appointment; or when you're deciding between a short nap and letting yourself sleep through more cycles overnight.

Who Benefits

Anyone trying to wake up feeling less groggy — students pulling irregular hours, shift workers and travelers adjusting their schedule, new parents grabbing sleep in short windows, and people simply trying to build a more consistent sleep routine — can use the cycle options to time sleep more deliberately than just aiming for "8 hours."

Frequently Asked Questions

Each option represents a different number of complete 90-minute sleep cycles (3 through 8). Waking up at the end of a cycle generally feels better than waking mid-cycle, so the calculator gives you a range — labeled Short, Good, Ideal, or Long — so you can pick the option that best fits your schedule while still landing on a cycle boundary.

Most people take roughly 10–20 minutes to actually fall asleep after getting into bed. The calculator uses 14 minutes as a reasonable average and adds it to your target bedtime so the cycle count is measured from when you're actually asleep, not from when you lie down.

90 minutes is an average — individual cycles can run anywhere from about 80 to 110 minutes, and they tend to shift slightly through the night. The calculator's suggestions are a useful starting estimate; if you consistently feel groggy at a suggested time, try adjusting your target by 15–20 minutes.

😴 Sleep Calculator