Jet lag recovery calculator
Last reviewed: 14 September 2026
Jet lag is a timing problem, not a tiredness problem — which is why sleeping more does not fix it and correctly timed daylight does.
Jet lag recovery calculator
How many time zones, and which way. You get an estimated recovery time and a day-by-day plan for before and after the flight.
How long does jet lag last?
Left to itself, the body clock shifts by roughly an hour a day. That gives the familiar rule of thumb of about a day per time zone — so a five-hour difference takes the best part of a working week to shake off, and a thirteen-hour difference can take a fortnight.
With well-timed light exposure, and melatonin used correctly, that rate can be considerably faster — published figures go up to three or four hours a day. Most of the difference between a miserable trip and a tolerable one comes down to light timing.
Why flying east is worse
The human circadian clock does not run to exactly 24 hours — it averages closer to 24.2. That small excess means your body finds it easier to delay than to advance: staying up later is working with the grain, and going to bed earlier is working against it.
Flying west asks you to delay, which your body is already inclined to do. Flying east asks you to advance. The practical result is that eastward recovery typically takes around half as long again as westward recovery across the same number of time zones.
East — light in the morning. You need to advance your clock, and morning light advances it.
West — light in the evening. You need to delay your clock, and evening light delays it.
Getting this backwards will shift you the wrong way, which is why people sometimes arrive and feel worse after three days rather than better.
Shifting before you fly
Every hour you shift before departure is an hour you do not have to shift on arrival, and it is far easier to do at home than in a hotel. Three days is the practical maximum for most people — beyond that the disruption to normal life outweighs the benefit.
- Flying east: go to bed and get up an hour earlier each day, and get bright light as early in the morning as you can manage.
- Flying west: go to bed and get up an hour later each day, and get light in the evening.
- Shift your meal times with your sleep. Food timing is a weaker cue than light, but it is not nothing.
On the plane and after you land
- Change your watch at the gate, and start thinking in destination time immediately. It sounds trivial and it genuinely helps.
- Sleep on the plane only if it is night at your destination. A long nap at the wrong time is worse than arriving tired.
- Stay up until a local bedtime on day one, however hard. If you must nap, keep it to 20 minutes.
- Get outside. Daylight is many times brighter than indoor lighting even under cloud, and light is the input your clock actually responds to.
- Keep caffeine to the local morning. It masks tiredness without moving your clock, and late caffeine makes the first nights worse.
- Expect day two or three to be the worst. Day one is usually carried by adrenaline and novelty.
- Melatonin can help, but the timing is everything — taken at the wrong hour it shifts you in the wrong direction. Worth asking a pharmacist or GP rather than guessing, particularly as availability differs between countries.
Short trips
If you are away for two or three days, adjusting fully is often the wrong goal — you will spend the whole trip adapting and then have to adapt back. For short trips it is usually better to stay on home time as far as the schedule allows, and to arrange meetings for the hours that overlap with your normal waking day.
Sources. Age-based recommendations are from the National Sleep Foundation’s sleep duration recommendations and the American Academy of Sleep Medicine’s consensus statements on sleep for healthy children and for adults. Sleep stage figures are from published polysomnography data. This page is general wellbeing information, not medical advice — speak to a GP or doctor about persistent sleep problems.
Common questions
How long does jet lag last?
Roughly a day per time zone crossed if you do nothing, because the body clock shifts about an hour a day on its own. Eastward travel takes around half as long again as westward. Well-timed light exposure can speed this up considerably.
Is jet lag worse going east or west?
East, for most people. The human circadian clock runs slightly longer than 24 hours, so delaying your sleep (flying west) works with the grain, while advancing it (flying east) works against it.
How do I get over jet lag quickly?
Start shifting your sleep a day or two before you fly, switch to destination time the moment you board, and get daylight at the right end of the day — morning light flying east, evening light flying west. Avoid long naps on the first day.
Should I sleep on the plane?
Only if it is night time at your destination. Sleeping on the plane when your destination is in daylight makes the adjustment harder rather than easier.
Does melatonin help with jet lag?
It can, but the timing determines whether it shifts you in the right direction or the wrong one. It is worth asking a pharmacist or GP about the correct timing for your route, and availability differs between countries.