Jet Lag Recovery Calculator
Your jet lag has a schedule. Most advice doesn’t give you one.
Pick your route and dates. Get an honest recovery estimate and a day-by-day plan with the actual clock times to seek and avoid light — the part “get some sunlight” leaves out.
Build my planGeneral travel guidance, not medical advice. This tool applies commonly cited circadian-rhythm principles to your route. Time-zone offsets are fixed standard-time approximations and ignore daylight saving. If you have a sleep disorder, take medication, are pregnant, or are traveling with a health condition, talk to a doctor before changing your sleep schedule or using melatonin.
Build your recovery plan
Set your route, arrival date, and the time you normally wake up. Pick the trip type — it changes whether the plan tells you to adjust at all. Everything is calculated in your browser.
Why flying east wrecks you and flying west doesn’t
Your body clock runs a little longer than 24 hours, so stretching a day is easy and compressing one is a fight. Same time difference, opposite experience — and it’s the single fact that should shape your plan.
Why eastward feels so much worse than westward
Here’s the part most jet lag advice skips: your internal body clock doesn’t run on exactly 24 hours. Left alone — in a room with no clocks or daylight — most people’s circadian rhythm drifts to something closer to 24 hours and 15–20 minutes. Your body finds it naturally easier to stretch a day than to compress one.
You land where the sun is “behind” where your body expects it. Staying up later and sleeping in is roughly what your clock already wants to do, so it drifts into place with less resistance.
You’re asking your body to fall asleep and wake up earlier than it’s used to, against its natural drift. A 6-hour eastward hop (New York to Paris) often feels rougher than a longer westward one.
There’s a twist for very long eastward trips. Past roughly 8–9 zones east, your clock gives up on advancing and drifts backward the long way instead — so New York to Tokyo (14 hours “ahead”) is handled by your body like a 10-hour westward delay. The calculator above detects that and flips the light advice accordingly.
What about melatonin?
Forums are full of people comparing melatonin, valerian, and over-the-counter “anti-jet-lag” tablets with no real consensus on what works. The one thing sleep researchers broadly agree on: timing matters more than the product or the dose. Melatonin is generally discussed as being taken a few hours before your target bedtime — the bedtime at your destination, not your origin — both in the pre-adjustment days and after you land.
Taken at the wrong time, it can shift your clock the wrong direction entirely. Dosing, timing, and whether melatonin is appropriate for you at all is a conversation for a doctor or pharmacist — especially if you’re on other medication, pregnant, or traveling with kids. The schedule above notes a rough melatonin window on adjustment days for reference only.
Is it even worth adjusting?
This is the question generic advice almost never asks. CDC travel guidance and most seasoned-traveler wisdom converge on a simple rule: if your trip is roughly 2–3 days or shorter, don’t bother adjusting. Fighting your clock for a 48-hour work trip usually costs more sleep than it saves — stay on home time as much as your itinerary allows, use strategic caffeine and short naps, and let your body reset once when you’re actually home.
For anything longer — a week, two weeks, a relocation — a real adjustment protocol pays off, because you’ll spend most of the trip feeling normal instead of jet-lagged. Pick the trip type in the calculator and the plan changes accordingly: short trips get an anchor-sleep strategy, longer trips get the full day-by-day schedule.
What generic jet lag advice gets wrong
“Get sunlight and drink water” isn’t wrong — it’s just not specific enough to act on. When you seek light depends entirely on which direction you flew and how many zones you crossed. Morning light helps an eastward traveler crossing 4 zones, but works against someone crossing 9 zones eastward, where midday light and a delay strategy are the better call. Generic advice also never tells you whether adjusting is worth attempting in the first place. A route-specific plan removes the guesswork so you’re not reverse-engineering chronobiology papers the night before a flight.
Frequently asked questions
How many days will jet lag actually last?
A commonly used rough estimate is about one day of recovery per time zone crossed traveling east, and roughly two-thirds of a day per zone traveling west, since westward shifts are physiologically easier. That’s a planning heuristic, not a guarantee — age, sleep debt, alcohol, and how strictly you follow a light schedule all move the number in real life.
Should I start adjusting before I leave, or wait until I arrive?
For trips long enough to justify full adjustment, many travelers start shifting their sleep time by 30–60 minutes per day toward the destination a few days before departure. If that’s not practical, adjusting entirely after arrival still works — it just takes a bit longer. When you pick “Long trip,” the calculator adds a short pre-flight shift plan.
Does the number of time zones matter more than direction?
Both matter, but direction changes how hard each zone feels. A 5-hour eastward trip and an 8-hour westward trip can feel similarly difficult, because eastward shifts fight your body’s natural tendency to drift later. “Only direction matters” is an oversimplification too — more zones is still more clock to move, either way.
Is jet lag worse on short trips?
The jet lag itself isn’t worse, but attempting to fully adjust for a short trip usually backfires — you disrupt your sleep trying to reset a clock you’re about to disrupt again on the way home. That’s why the 2–3 day rule of thumb exists: below that trip length, staying on home time is usually the better trade.
What if I can’t get real daylight at the right time?
Daylight is strongest, but a bright indoor environment, a light box, or even just being near a window helps. What matters more is avoiding bright light during the “avoid” window — dim the room, and wear sunglasses outdoors if you land during that window.