Healthy sleep, explained
Sleep science you can use tonight
Clear, sourced guides to healthy sleep and free calculators for bedtimes, wake-up times, naps, caffeine and jet lag. Every page is fact-checked against its sources.
Calculators All calculators →
Night Shift Sleep Calculator: When to Sleep Before and After Your Shift
Enter your night shift times and commute to get a daytime sleep window, an optional pre-work nap, a caffeine cut-off, and a plan for night one and days off.
CalculatorSleep Efficiency Calculator: What Percentage of Your Time in Bed You Sleep
Work out your sleep efficiency from one night or a week of sleep diary averages, see whether it is in the normal range, and learn how CBT-I uses the number.
CalculatorCaffeine Calculator: How Much Caffeine Is Left at Bedtime
Add your coffees, teas or energy drinks and your bedtime to estimate how much caffeine is still in your body when you lie down, and when it fades.
CalculatorChronotype Calculator: Your Mid-Sleep Point and Social Jet Lag
Turn your real workday and free-day sleep times into a chronotype number (corrected mid-sleep) and your social jet lag, using the method sleep researchers use.
CalculatorHow Much Sleep Do I Need? Sleep Need Calculator by Age
Find the recommended hours of sleep for your age, a personal starting target based on how you sleep and feel now, and the bedtime that fits your alarm.
CalculatorJet Lag Calculator: Your Personal Sleep and Light Plan
Enter the time difference and your usual sleep times for a day-by-day trip plan: when to seek light, when to avoid it, and how long adapting may take.
Guides All guides →
How to Adjust Your Sleep to Daylight Saving Time (Spring and Fall)
Adjust to daylight saving time by shifting bedtime 15 to 20 minutes a night for a few nights before the change. Why spring is harder and how long it takes.
GuideHow to Switch From Night Shift Back to a Day Schedule
After your last night shift, take a short morning sleep, get afternoon daylight and go to bed at a normal hour. Here is how to switch back, days off included.
GuideIs It Bad to Go to Bed at 2 a.m. Every Night?
A 2 a.m. bedtime isn't harmful in itself if you still sleep 7+ hours at steady times. Trouble starts with early alarms, drifting schedules and missed daylight.
GuideIs It Better to Sleep 2 Hours or Stay Up All Night?
For most people, a short sleep beats none: even 90 minutes to 2 hours helps alertness and memory. How to pick 90 minutes vs 3 hours and time the alarm well.
GuideIs Jet Lag Worse Flying East or West?
Flying east is usually harder, because your body clock runs slightly longer than 24 hours and finds it easier to stay up late than go to bed early.
GuideShould You Sleep Before a Night Shift? (Including Your First One)
Yes: a planned nap of 1.5 to 3 hours in the afternoon or early evening helps you stay alert overnight. Here is how to time it, even for your first night.
GuideWhy Do I Sleep Better on the Couch Than in My Bed?
If you doze off easily on the sofa but lie awake in bed, your bed may have become a cue for being awake. Here is why that happens and how to retrain it.
GuideWhy Do I Wake Up Right Before My Alarm?
Your body can learn when the alarm is due and start a stress-hormone rise about an hour before it. Why it happens, why you may still feel tired, and what to do.
GuideWhy Do I Wake Up at 3 a.m. After Drinking?
Waking at 3 or 4 a.m. after drinking is a rebound: as alcohol wears off, sleep turns light, your heart races and your bladder fills. Here is what helps.
How SleepGuru works
- Sources you can check. Every claim that matters links to its source: health agencies, sleep medicine societies and peer-reviewed research.
- Fact-checked, then reviewed. Every page is checked against its sources before it goes live, then reviewed by John Smit. Our editorial policy explains the whole process, including how we use AI.
- Calculators show their method. Each one explains its formula, its assumptions and when the result is not reliable.