Jet Lag Calculator: Time Zones Crossed, Recovery Days and Sleep Plan

How the jet lag estimate works

Jet lag happens when your body clock no longer matches local time after a fast trip across time zones. The calculator takes the clock difference between your two airports on your travel date, including daylight saving time where it applies in the US, Europe, Australia and New Zealand. It then counts the zones crossed and sets the direction: clocks ahead at your destination is eastward, clocks behind is westward.

Recovery time follows a rule of thumb. Wikipedia's jet lag article notes that recovery takes on average about one day per hour of time zone change, and that most travelers find eastward travel harder. So the tool uses 1 day per zone going east and 1 day per 1.5 zones going west. Both numbers are editable, so you can match your own experience. A worked example: New York to London in December is 5 zones east, which gives about 5 days. The return trip, 5 zones west, gives about 3.3 days.

The sleep plan follows the same source: shifting your sleep schedule by 1 to 2 hours before departure to match the destination may shorten jet lag. Enter your usual bedtime, the number of nights you can shift and the hours per night. The plan lists a bedtime for each night, earlier for eastward trips and later for westward ones, and shows how many hours remain to adjust after landing. Morning light helps going east. Evening light helps going west.

Treat every figure here as an average, not a promise. Age, sleep debt, trip length and how you spend the first day all change recovery. Short hops of one or two zones rarely need a plan. For longer trips, pair this page with the flight time calculator to see how long you will be in the air and the time zone converter for exact clock gaps. This is general information, not medical advice.

Where these numbers come from

The formulas and default values in this calculator are based on:

• Wikipedia, Jet lag (recovery of about one day per hour of time zone change, harder eastward, 1 to 2 hour pre-travel sleep shift, morning light eastward and evening light westward). Note: the 1.5 zones per day westward rate, the UTC offsets and the daylight saving rules are planning approximations you can adjust

This is a planning estimate, not medical, legal or immigration advice. Fees, allowances, limits and entry rules change, so confirm the figures with your airline, cruise line, customs agency or the official government source before you book or travel, and follow their rules if they differ from this page.