What Time Should I Go to Bed? Calculator + Complete Guide

The exact time you should go to bed depends on three variables: when you need to wake up, how many 90-minute sleep cycles you want to complete, and how long you take to fall asleep. Our calculator handles all three. Here's the answer for the most common wake times — and the science behind it.

Bedtime Calculator: Get Your Answer Now

Quick Answer: Bedtimes for Common Wake Times

Here are the recommended bedtimes (5 cycles / 7.5 hours) for the most common wake times. All times include 15 minutes to fall asleep:

Based on 5 complete 90-minute cycles (7.5 hours). For 6 cycles (9 hours), add 90 minutes to each bedtime.

Why These Specific Times?

Sleep moves through 90-minute cycles. At the end of each cycle, you briefly return to light sleep before beginning the next. Waking at this transition point — rather than mid-cycle — is the difference between feeling refreshed and feeling groggy.

The formula: Bedtime = Wake time − (cycles × 90 min) − 15 min

The 15-minute offset accounts for sleep onset latency — the average time it takes to fall asleep after lying down. If you consistently take longer (30+ minutes), adjust your bedtime 15 minutes earlier.

How Many Cycles Should You Choose?

• 6 cycles (9 hours): Optimal for athletes, people under stress, or those with high sleep needs. Add 90 minutes to the bedtimes above.
• 5 cycles (7.5 hours): Recommended for most healthy adults. The times in the table above.
• 4 cycles (6 hours): Minimum — use only when necessary. Subtract 90 minutes from the bedtimes above.

What If You Can't Hit the Exact Time?

If you can't go to bed at exactly the calculated time, here's the rule: earlier is better than later. Going to bed 15 minutes before the optimal time puts you in Stage 1 or early Stage 2 when your alarm goes off — still light sleep, modest impact. Going to bed 30-45 minutes after the optimal time puts your alarm mid-cycle, potentially interrupting deep sleep.

Example for a 7 AM wake-up: 11:15 PM is optimal. 11:00 PM is fine. 11:45 PM is problematic.

The Most Important Rule: Consistency

Once you've found your ideal bedtime, the most powerful thing you can do is maintain it consistently — including weekends. Varying your bedtime by more than 1 hour creates social jet lag, a form of circadian disruption associated with obesity, depression, and cardiovascular disease.

Your wake time is the most important anchor. Keep it consistent 7 days a week, and your bedtime will naturally stabilize. The circadian rhythm is strengthened by regularity.

Signs Your Bedtime Is Right

• You fall asleep within 10-20 minutes of lying down
• You wake up before or around your alarm most mornings
• You feel alert within 15-30 minutes of waking without caffeine
• You maintain consistent energy throughout the day
• You feel genuinely sleepy at your target bedtime

Signs Your Bedtime Needs Adjustment

• Can't fall asleep at your bedtime: Your circadian rhythm may be set later. Try morning light exposure and evening light reduction for 1-2 weeks.
• Wake up groggy despite the right bedtime: You may be waking mid-cycle. Try adjusting your bedtime by 15 minutes in either direction.
• Always tired despite the right bedtime: You may need more cycles. Try 6 cycles (9 hours) instead of 5.

Sources: Carskadon & Dement (2011). Normal human sleep. Principles and Practice of Sleep Medicine. Watson et al. (2015). Recommended Amount of Sleep for a Healthy Adult. Sleep.