How does the calculator build your plan?
- Finds the shift. It compares both time zones on your travel dates, including daylight saving time and the date line, and picks the faster direction (for 10+ hours east, it moves clocks later instead).
- Estimates each body clock. From each person's usual wake time it estimates their body-temperature low point, which sets when light helps and when it hurts.
- Schedules every day. Bedtimes, wake times, light to seek and avoid, naps, meals and optional melatonin, with smaller steps for kids, from the head start until everyone is on local time.
Read the full methodology and sources.
Is jet lag worse flying east or west?
East is harder: body clocks must move earlier, which happens more slowly.
| Flying east | Flying west | |
|---|---|---|
| Body clock must… | Move earlier (advance) | Move later (delay) |
| Typical speed | About 1 hour a day | About 1–1.5 hours a day |
| First nights feel like | Can't fall asleep, hard to wake | Sleepy early evening, up at 4–5 AM |
| Get bright light | Late morning and midday at first | Late afternoon and evening |
| Avoid bright light | Early morning for the first days | Early morning before the planned wake time |
| Head start at home | Bedtime and wake-up earlier | Bedtime and wake-up later |
| Melatonin (adults; kids only with pediatrician OK) | Can help at the new bedtime | Usually not needed |
| Example | US → Europe | Europe → US, US → Hawaii or Asia |
How many days does jet lag last by time difference?
| Time difference | East, no prep | East, 2-day head start | West, no prep | West, 2-day head start |
|---|---|---|---|---|
| 2 hours | 2 | 1 | 2 | 1 |
| 3 hours | 3 | 1 | 2 | 1 |
| 4 hours | 4 | 2 | 3 | 2 |
| 5 hours | 5 | 3 | 4 | 2 |
| 6 hours | 6 | 4 | 4 | 3 |
| 7 hours | 7 | 5 | 5 | 4 |
| 8 hours | 8 | 6 | 6 | 4 |
| 9 hours | 9 | 7 | 6 | 5 |
| 10 hours | 10* | 8* | 7 | 6 |
| 11 hours | 9* | 8* | 8 | 6 |
| 12 hours | 8* | 7* | 8* | 7* |
See the time difference chart for popular routes and how long jet lag lasts for kids.
Popular family routes
- New York → London
- Los Angeles → Tokyo
- Denver → London
- Chicago → Paris
- New York → Rome
- San Francisco → Sydney
- Boston → Dublin
- Los Angeles → Honolulu
- London → Orlando
- Seattle → Tokyo
- Miami → Madrid
- New York → Lisbon
Guides by age and situation
- With a baby (0–12 months)
- With a toddler (1–3)
- With kids 4–8
- With teens
- Flying east with kids
- Flying west with kids
- How long jet lag lasts
- Melatonin for kids
- Time difference chart
- Jet lag coming home
- Sleep kit checklist
- Jet lag not working?
Frequently asked questions
How does the family jet lag calculator work?
Enter where you fly from and to, who is traveling and (optionally) your flight times. It estimates each person's body-clock low point from their usual wake time, then schedules bedtimes, light, darkness, naps and optional melatonin to move everyone's clock toward destination time, following published circadian research.
How many days does jet lag last for kids?
About one day per time zone after flying east and a little less after flying west. A 2–3 day head start at home can cut 1–2 days.
Is jet lag worse flying east or west?
East. The body clock has to move earlier, which it does more slowly (about 1 hour a day) than moving later (about 1–1.5 hours a day).
Should kids nap when they have jet lag?
Yes, but short and early: 20–30 minutes for older kids and adults, up to 45 minutes before 2 PM for kids 4–8. Toddlers keep naps on local time and end the last nap by about 4 PM.
Can kids take melatonin for jet lag?
Only after talking with your pediatrician. If approved, a low dose (often 0.5–1 mg) 30–90 minutes before the new bedtime for a few nights after flying east is typical. Not for babies or toddlers.
Should we start adjusting before the trip?
Yes, if you can. Shift bedtime and wake-up 1 hour a day for adults and 15–30 minutes a day for kids, for 2–3 days before you fly.
What if our trip is only a few days?
For trips of 3 days or less, the plan keeps you close to home time and shifts only part of the way, so there is less to undo when you get home.
Is my data saved?
No. The plan is calculated in your browser. The share link stores your inputs in the URL so anyone you send it to sees the same plan.
Sources
- CDC Yellow Book 2026: Jet Lag Disorder. US Centers for Disease Control and Prevention guidance for travelers and clinicians.
- Eastman CI, Burgess HJ. How to travel the world without jet lag. Sleep Med Clin, 2009. The light-timing and pre-flight shifting method this calculator follows.
- Burgess HJ et al. Preflight adjustment to eastward travel: 3 days of advancing sleep with and without morning bright light. J Biol Rhythms, 2003. Shifting sleep 1 hour a day before an eastward flight.
- Eastman CI et al. Advancing circadian rhythms before eastward flight: a strategy to prevent or reduce jet lag. Sleep, 2005. How fast body clocks can be moved earlier before travel.
- American Academy of Pediatrics (HealthyChildren.org): Melatonin and children's sleep. Pediatric guidance on melatonin dose, timing and safety.
- American Academy of Sleep Medicine: Melatonin use in children and adolescents (health advisory). Advises involving a health care professional before giving children melatonin.
- Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews. Systematic review of melatonin for jet lag in adults.
How we turn this research into plans: methodology.