Jet Lag Recovery Calculator
Adjust days from zones and direction.
What it does
Jet lag is a clock mismatch: the body keeps home time while the destination runs another. Eastward jumps compress the day and hurt more; westward stretches it and eases faster.
The tool above takes zones crossed with direction. It returns recovery days at CDC pace with the one per zone rule beside it.
The defaults cross 6 zones eastward: about 6 days both ways. Westward the same 6 zones need about 4 days at CDC pace against 6 by the simple rule.
Paces follow CDC Yellow Book jet lag guidance with sleep educator guidance matching: about an hour a day east, an hour and a half west, one day per zone as the plain rule.
How to use
- Enter time zones crossed.
- Pick eastward or westward.
- Read CDC pace days first.
- Read one per zone beside it.
- Shift sleep an hour daily pre trip.
- Keep home time on short trips.
Formula
- zones
- Time zones crossed, 2 plus counts.
- 1 / 1.5
- CDC daily shift hours east / west.
- 1x
- Plain one day per zone rule.
Trips under 2 days should keep home schedule instead of adapting. Age, pre shifting, light timing, and naps move real recovery around these lines.
Worked example
Example: 6 zones east
Defaults: 6 zones crossed, eastward.
- CDC: 6 / 1 = 6 days.
- Simple: 6 x 1 = 6 days.
- Tool shows 6 days CDC pace, 6 one per zone.
- West check: 6 / 1.5 = 4 days CDC.
- Short trips keep home time instead.
Reference table
| Trip | CDC pace | One per zone |
|---|---|---|
| 3 zones west | 2 days | 3 days |
| 6 zones east | 6 days | 6 days |
| 6 zones west | 4 days | 6 days |
Limits
- Averages, not personal clocks.
- Under 2 days: do not adapt.
- Light mistimed worsens lag.
- Age slows adjustment.
Common mistakes
- Adapting on overnight trips.
- Bright light at wrong hours.
- Long daytime naps on arrival.
- Heavy alcohol as sleep aid.
- Same plan east and west.
Try it yourself
Quick checks. Answers sit tucked under each question.
3 zones west?
2 days CDC pace, 3 by the simple rule.
9 zones east?
9 days both ways.
Short trip rule?
Under 2 days, keep home schedule.
Questions
How long does jet lag last?
About a day per zone east, two thirds that west.
Why east harder?
Advancing the clock fights biology more than delaying.
Melatonin help?
Low timed doses can help; high doses and sedatives backfire.
Naps allowed?
Short 20 to 30 min naps; long day sleep harms nights.
Pre shift work?
Move sleep an hour daily for 2 to 3 days pre trip.
Kids different?
Same clock rules with earlier bedtimes doing the work.