Calculate your perfect bedtime, optimal wake-up times, and sleep cycles based on 90-minute REM science. Includes Jet Lag recovery and Nap optimizer.
Choose your mode: Bedtime, Wake-Up, Jet Lag recovery, or Nap optimizer.
Each sleep cycle lasts ~90 minutes. Waking at the end of a cycle means you feel alert, not groggy.
Smart day-by-day adaptation plan based on time zone difference and eastward vs westward travel.
Scientifically timed nap windows — from 10-min power naps to full 90-min recovery naps.
Tailored recommendations for infants to seniors, aligned with NHS and NSF sleep guidelines.
Real-time clock with sleep phase awareness — knows if it's your ideal bedtime window right now.
All calculations run in your browser. No data stored, no accounts needed, no tracking.
Select Bedtime, Wake-Up, Jet Lag, or Nap mode based on what you need to calculate.
Set your target wake-up time, bedtime, arrival time, or nap start. All fields have smart defaults.
Click Calculate and get science-backed times based on 90-minute sleep cycles and your age group.
Pick the recommended time (highlighted), set your alarm, and wake up at the end of a full sleep cycle.
Sleep is not merely rest — it is one of the most active biological processes your body undergoes every night. A Sleep Calculator removes the guesswork by aligning your bedtime and alarm to the natural rhythm of your brain, specifically the 90-minute sleep cycle. Each cycle moves through four stages: N1 (light sleep), N2 (baseline sleep), N3 (deep/slow-wave sleep), and REM (rapid eye movement). Waking mid-cycle — especially during deep sleep — causes that disorienting, heavy feeling known as sleep inertia. Our calculator ensures you surface gently at the end of a cycle, so you feel alert from the first moment.
The National Sleep Foundation recommends adults aim for 7 to 9 hours per night, which equates to 5 or 6 complete 90-minute cycles. However, it is not just about total hours — cycle alignment matters enormously. Studies show individuals who wake at a natural cycle boundary report significantly higher alertness scores than those who sleep longer but are woken mid-cycle. This is the core science behind our bedtime calculator and wake-up time calculator.
If you have recently crossed time zones, our Jet Lag Sleep Calculator can be a genuine lifesaver. Jet lag occurs when your circadian rhythm — your body's internal clock — falls out of sync with the local day-night cycle. Eastward travel is typically harder to recover from because you are effectively "losing" time. The general rule is one day of recovery per hour of eastward time zone shift. Our tool generates a personalised day-by-day sleep adjustment plan, gradually shifting your target bedtime and wake-up window until full re-synchronisation.
Strategic napping is another overlooked sleep tool. A 20-minute power nap taken before entering deep sleep boosts alertness and mood without causing post-nap grogginess. A 90-minute full-cycle nap includes REM sleep and is ideal for creative work, learning consolidation, and muscle recovery. Our Nap Calculator identifies the precise wake-up window for your chosen nap goal, whether you want a quick refresh or a restorative afternoon sleep session.
Healthy sleep hygiene reinforces whatever schedule our calculator recommends. Key practices include maintaining a consistent sleep and wake time every day (including weekends), keeping your bedroom cool (around 18–20°C), avoiding blue-light screens 60–90 minutes before bed, limiting caffeine after 2 pm, and using relaxation techniques like deep breathing or progressive muscle relaxation. Combining these habits with our calculator's cycle-aligned schedule creates a powerful foundation for long-term sleep quality, cognitive performance, and overall health.
Keep room at 18–20°C for optimal sleep onset.
Avoid blue light 60–90 min before bedtime.
Stop caffeine by 2 pm. It has a 5–6 hour half-life.
Same wake time every day — even weekends.
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