Your brain sets a timer
Right after you fall asleep your body releases adenosine and melatonin dips—part of why that first ~14-minute wind-down matters for timing cycles.
Wind-down window
Sleep Calculator – Best Bedtime & Wake-up Times
Set your time & options
Tip: People often feel best after 5–6 cycles (~7.5–9 hours). Your ideal may vary.
Results will appear here.
Keyboard: Enter to calculate • Ctrl/Cmd+K focuses site search
How it works
Sleep tends to occur in ~90-minute cycles. Waking up at the end of a cycle can feel easier than waking mid-cycle. This calculator adds a short buffer (default 14 minutes) for the time it typically takes to fall asleep, then suggests bedtimes or wake-up times that land near the end of cycles.
FAQ
What assumptions does this calculator use?
We use 90-minute cycles and a default 14-minute fall-asleep buffer. You can change the buffer to suit you.
How many cycles should I target?
Many adults prefer 5–6 cycles (about 7.5–9 hours), but sleep need is individual. Use these times as gentle suggestions.
Is my data private?
Yes. Everything runs locally in your browser; no data is uploaded.
Additional Information About Sleep Cycles
This sleep calculator is designed to help you pick a bedtime or wake-up time that lines up with your natural sleep cycles. Most people move through repeating cycles that include light sleep, deep sleep, and REM (rapid eye movement). A full cycle averages about 90 minutes, and waking at the end of a cycle often feels smoother than waking in the middle of one. That’s why a bedtime calculator can be so useful when you want to feel more alert in the morning.
The calculator also accounts for the time it takes to fall asleep. Even if you go to bed at a specific time, your body needs a short wind-down before you actually drift off. By adding a small buffer, the suggested sleep schedule better reflects real-life timing. Think of it as a gentle guide that combines sleep cycle timing with a realistic bedtime routine, not a strict rule you have to follow.
How to Use This Sleep Calculator
- Choose whether you want to plan a bedtime or a wake-up time.
- Enter the time you need (or use the current time option for quick results).
- Adjust the fall-asleep buffer if your routine is longer or shorter than average.
- Click calculate to see suggested times that end at the close of a sleep cycle.
- Pick the option that fits your schedule, ideally aiming for 5–6 full cycles (about 7.5–9 hours).
Real-World Use Cases
This tool is helpful for early work or school start times, travel days, or nights when you want to maximize rest without oversleeping. For example, if you need to wake at 6:30 AM, the calculator shows several bedtime options that align with your sleep cycle length. If you’re going to bed now, it can also suggest wake-up times that may leave you feeling more refreshed.
Sleep Quality and Healthy Habits
A good sleep schedule works best alongside healthy sleep hygiene. Limiting caffeine late in the day, reducing bright screens before bed, and keeping your room cool and dark can improve how restorative each cycle feels. Your circadian rhythm, or internal body clock, also matters—consistent sleep and wake times tend to make falling asleep easier over time.
Keep Expectations Realistic
Sleep cycles can vary from person to person and from night to night, so the suggested times are approximate. Use the results as a starting point, and adjust based on how you feel. If sleep problems are frequent or severe, it’s best to talk with a healthcare professional.
5 Fun Facts about Sleep Cycles
Cycle length isn’t fixed
The “90 minutes” is an average—real cycles swing from 80–110 minutes. Early cycles pack more deep sleep; later ones tilt toward REM.
Varies by person
Light decides melatonin
Blue light nudges your internal clock later. Just 30–60 minutes of dim light before bed can make hitting cycle endpoints noticeably easier.
Light hygiene
REM stacks at the end
Most REM sleep clusters in the final cycles—skipping the last cycle can trim dreaming time even if total hours look okay.
Dream load
90 minutes isn’t magic
6 cycles at 90 minutes is 9 hours, but many people feel fine at 5 cycles (~7.5 hours) if their wake time is consistent.
Personal tuning