Bedtime Calculator — Sleep and Wake Up Well

If you know what time you need to wake up, you can figure out the best time to go to bed. The calculator works backward from your wake-up time, closing sleep cycles of about 90 minutes and setting aside 15 minutes to fall asleep. Enter your wake-up time.

How the calculator arrives at these times

The starting point is the time you need to wake up. From there, the calculator subtracts blocks of 90 minutes (one complete sleep cycle) plus 15 minutes, the average time it takes to fall asleep after lying down. The result is several possible bedtimes, each corresponding to a whole number of cycles.

For example, to wake up at 6:00 AM: sleeping around 10:15 PM closes 5 cycles (7h30 of sleep); sleeping at 8:45 PM closes 6 cycles (9h00); sleeping at 11:45 PM closes 4 cycles (6h00). Pick the time that fits your routine and still guarantees the 7 to 9 hours recommended for adults.

Why closing cycles helps you wake up better

Throughout the night, sleep alternates between light and deep phases within each cycle. Waking up at the end of a cycle, when sleep is more superficial, tends to be much gentler than being pulled out of deep sleep in the middle of it. That’s why sometimes you wake up rested with fewer hours, and other nights you wake up wrecked with more: it’s not just about quantity, it’s also about the moment the alarm goes off.

Regularity matters more than the exact time

The body has an internal clock that learns from repetition. Going to sleep and waking up at the same times — including weekends, as much as possible — keeps that clock more stable and helps you fall asleep faster and wake up with less effort. Some habits that help you stick to the chosen time:

• Reduce light and screens in the last hour before bed
• Avoid coffee, energy drinks, and alcohol at night
• Keep the bedroom dark, quiet, and cool
• Don’t use the bed to work or watch videos for hours

Need the other direction?

If your starting point is your bedtime and you want to know when to wake up, use the wake-up time calculator. To understand the logic behind the 90 minutes, see the sleep cycle calculator, and to measure how much you slept in a given night, the sleep duration calculator.

This content is for informational purposes and does not replace medical evaluation. The times are a reference based on the 90-minute average per cycle, which varies from person to person.