Sleep Calculator
Find the best time to go to bed and wake up refreshed
Each sleep cycle is approximately 90 minutes
Go to bed at...
(includes ~15 min to fall asleep)cycles
9.0 hours
09:45 PM
cycles
7.5 hours
11:15 PM
cycles
6.0 hours
12:45 AM
How Sleep Cycles Work
Your sleep follows 90-minute cycles through light sleep, deep sleep, and REM. Waking up at the end of a cycle (rather than mid-cycle) helps you feel more refreshed and alert.
Sleep Better Tonight
Light Dinner
Keep dinner light and finish 2-3 hours before bed for easier sleep.
Set a dinner deadline time
Caffeine Cutoff
Avoid tea/coffee after 2-3 PM to reduce sleep latency.
Switch to herbal tea or water
Wind Down
Dim lights and avoid screens 30 minutes before bed.
Set an "offline" alarm
Quick Sleep Facts
Hours recommended
For most adults (18-64)
Minutes per cycle
Average sleep cycle length
Minutes to fall asleep
Average sleep latency
How to Use This Sleep Calculator
Enter the time you need to wake up, and the sleep calculator instantly shows you the best times to go to bed. It works by counting backward in 90-minute sleep cycles and adding 15 minutes of average sleep latency (the time it takes to fall asleep). The goal is to wake up at the end of a complete cycle so you feel alert instead of groggy.
What Are Sleep Cycles?
Every night your body moves through repeating sleep cycles, each lasting about 90 minutes. A single cycle includes four stages:
- Stage 1 (Light Sleep) — Transition from wakefulness to sleep. Lasts a few minutes.
- Stage 2 (Light Sleep) — Heart rate slows, body temperature drops. Makes up about 50% of total sleep.
- Stage 3 (Deep Sleep) — The most restorative stage. Hard to wake from, important for physical recovery and immune function.
- REM Sleep — Brain activity increases, dreams occur. Critical for memory consolidation and learning.
Waking up during deep sleep (Stage 3) causes sleep inertia — that heavy, disoriented feeling. This sleep calculator helps you avoid that by aligning your alarm with the lighter phases between cycles.
How Much Sleep Do You Need?
| Age Group | Recommended Hours | Sleep Cycles |
|---|---|---|
| Newborn (0–3 months) | 14–17 hours | — |
| Infant (4–11 months) | 12–15 hours | — |
| Toddler (1–2 years) | 11–14 hours | — |
| School-age (6–13 years) | 9–11 hours | 6–7 cycles |
| Teenager (14–17 years) | 8–10 hours | 5–7 cycles |
| Adult (18–64 years) | 7–9 hours | 5–6 cycles |
| Older Adult (65+) | 7–8 hours | 5 cycles |
Tips for Better Sleep
- Stick to a schedule — Go to bed and wake up at the same time every day, even on weekends.
- Limit screen time — Blue light from phones and laptops suppresses melatonin. Stop screens 30–60 minutes before bed.
- Watch your diet — Avoid heavy meals, caffeine, and alcohol close to bedtime. Finish dinner at least 2–3 hours before sleep.
- Keep your room cool and dark — A temperature of 18–22°C and blackout curtains help your body produce melatonin.
- Exercise regularly — Even 20–30 minutes of moderate exercise improves sleep quality, but avoid intense workouts within 2 hours of bedtime.
- Manage stress — Try deep breathing, journaling, or light stretching before bed to calm your mind.
How does this sleep calculator work?
Enter the time you need to wake up, and the calculator counts backward in 90-minute sleep cycles (plus about 15 minutes to fall asleep) to suggest the best bedtimes. Each result aligns your wake-up with the end of a full cycle so you feel refreshed instead of groggy.
How many sleep cycles do I need?
Most adults feel best after 5 or 6 complete sleep cycles, which gives you 7.5 to 9 hours of sleep. Four cycles (6 hours) is the minimum for functioning, but consistently sleeping less than 5 cycles may affect your health and alertness.
What is a sleep cycle?
A sleep cycle is a roughly 90-minute sequence that includes light sleep, deep sleep (slow-wave sleep), and REM sleep. Your body typically goes through 4 to 6 of these cycles per night. Deep sleep is most concentrated in earlier cycles, while REM sleep increases in later cycles.
Why do I feel tired even after 8 hours of sleep?
Waking up in the middle of a sleep cycle — especially during deep sleep — can leave you feeling groggy (sleep inertia). This calculator helps you time your sleep so you wake up at the end of a cycle. Other causes include inconsistent sleep schedules, caffeine, screen time before bed, or an underlying sleep disorder.
What is the best time to sleep in India?
For most Indian adults who wake up between 6:00–7:00 AM, going to bed between 10:00 PM and 11:00 PM is ideal. This allows 5–6 full sleep cycles. Ayurveda also recommends sleeping before 10 PM during the Kapha period for deeper rest.
Does this sleep calculator work for naps?
This calculator is designed for full-night sleep. For naps, aim for either 20 minutes (power nap — light sleep only) or 90 minutes (one full sleep cycle). Avoid naps longer than 30 minutes but shorter than 90 minutes, as waking mid-cycle can make you feel worse.
How much sleep do children and teenagers need?
Newborns need 14–17 hours, toddlers 11–14 hours, school-age children 9–11 hours, and teenagers 8–10 hours. Adults (18–64) need 7–9 hours, while older adults (65+) need 7–8 hours. These are guidelines — individual needs may vary.
Is this sleep calculator medically accurate?
This calculator uses the widely accepted 90-minute sleep cycle model and 15-minute average sleep latency. While these are good averages, individual cycle lengths can range from 70 to 120 minutes. It is a helpful planning tool, not a medical device. Consult a doctor if you have persistent sleep problems.