Jet Lag Calculator: Time Zone Difference and Sleep Plan
Works out the time difference, a rough jet lag recovery time and a bedtime plan for before and after your flight.
Free · runs in your browser · nothing is sent anywhere
This calculator turns two UTC offsets, your usual bedtime and the flight direction into an hour difference, a rough recovery estimate and a night-by-night bedtime plan. It helps you decide whether to start shifting your sleep before you fly, and how many days to leave free for adjusting.
How it works
- Enter your home and destination UTC offsets, and tick daylight saving if it applies on your dates.
- Set your usual bedtime and the flight direction (or leave it on auto).
- Choose how many days before departure you can shift your sleep.
- Read the hour difference and recovery estimate, then follow the bedtime tables.
Formula: hours = (destination UTC offset + destination daylight saving) − (home UTC offset + home daylight saving), wrapped by flight direction. recovery days = ceil(hours × 1) westbound, ceil(hours × 1.5) eastbound. Bedtime moves 1 hour per night, before departure first, then after arrival.
The 1.5 factor for eastbound is this tool's assumption for "more when flying east", not a measured figure. This is general information, not medical advice; ask a doctor if you have a sleep or health condition.
Frequently asked questions
Why is flying east usually harder?
Flying east asks your body to fall asleep earlier than it wants to, which most people find harder than staying up later. That is why the tool uses a longer rough recovery for eastbound trips.
Where do I find my UTC offset?
Look up your city's current offset on a time zone converter or the country's official time source. Check whether daylight saving applies on your travel dates, since the change dates differ by country.
Is the recovery time accurate?
No, it is a rule of thumb. Age, sleep on the flight, light exposure and the schedule of your first days all change how long it takes.