Jet Lag Recovery Calculator
How long jet lag will last and how to adjust.
Enter your values
Enter the time zones crossed you are working with.
Choose one of: Eastward, Westward.
Enter the days before departure to prepare you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Estimated recovery
- 11.9 days
- Direction difficulty
- Harder — you must sleep earlier
- Pre-trip shift per day
- 2.7 hours
- Best light exposure
- Morning light on arrival
- Avoid light
- Late evening
| Tactic | Effect |
|---|---|
| Shift bedtime before travel | Cuts recovery by 1–2 days |
| Time light exposure | Strongest single zeitgeber |
| Skip alcohol in flight | Protects sleep quality |
| Eat on destination schedule | Aligns peripheral clocks |
Quick answer
The body re-syncs about one time zone per day travelling west and roughly two-thirds of that going east.
Days ≈ zones ÷ 1.0 (west) or zones ÷ 0.67 (east)
At a glance
| What it does | How long jet lag will last and how to adjust. |
|---|---|
| Category | Travel |
| Inputs needed | Time zones crossed, Direction, Days before departure to prepare |
| Main output | Estimated recovery |
| Formula | Days ≈ zones ÷ 1.0 (west) or zones ÷ 0.67 (east) |
| Cost | Free — no sign-up, no download |
How to use the Jet Lag Recovery Calculator
- 1Enter how many time zones you're crossing.
- 2Choose the direction of travel.
- 3Set how many days you can prepare beforehand.
Inputs explained
- Time zones crossed
- Enter the time zones crossed you are working with.
- Direction
- Choose one of: Eastward, Westward.
- Days before departure to prepare
- Enter the days before departure to prepare you are working with.
Worked example
Using the values the calculator loads with:
Inputs
- Time zones crossed8
- DirectionEastward
- Days before departure to prepare3
Results
- Estimated recovery11.9 days
- Direction difficultyHarder — you must sleep earlier
- Pre-trip shift per day2.7 hours
- Best light exposureMorning light on arrival
- Avoid lightLate evening
Frequently asked questions
Why is eastward travel worse?
Your natural body clock runs slightly longer than 24 hours, so delaying sleep is easier than advancing it.
Does melatonin help?
Low doses timed correctly can advance the clock for eastward travel; timing matters far more than dose.
What do I need to enter into the Jet Lag Recovery Calculator?
Just 3 values: time zones crossed, direction, days before departure to prepare. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Jet Lag Recovery Calculator work out the answer?
The body re-syncs about one time zone per day travelling west and roughly two-thirds of that going east. It applies the formula Days ≈ zones ÷ 1.0 (west) or zones ÷ 0.67 (east) and shows the working so you can check each step by hand.
Is the Jet Lag Recovery Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.