Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Days to fully adjust
8.0
Days with pre-trip shifting
6.5
Pre-flight plan
Go to bed 30–60 min earlier each night
Light exposure
Seek morning light on arrival
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter time zones crossed.
- 2Enter direction.
- 3Enter days you can prep before flying.
- 4Read your days to fully adjust on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
The body clock resets about one time zone per day, faster going west than east. This estimates recovery and a pre-flight shifting plan.
Worked example
Using the values the calculator loads with:
Inputs
- Time zones crossed: 8
- Direction: Eastward (harder)
- Days you can prep before flying: 3
Results
- Days to fully adjust: 8
- Days with pre-trip shifting: 6.5
- Pre-flight plan: Go to bed 30–60 min earlier each night
- Light exposure: Seek morning light on arrival
What each field means
Inputs
- Time zones crossed
- The time zones crossed used in the calculation. Starts at 8 so you have a working example on load. Accepted range: 0–14.
- Direction
- Pick the option that matches your situation — the maths changes per option. Choices: Eastward (harder), Westward (easier).
- Days you can prep before flying
- The days you can prep before flying used in the calculation. Starts at 3 so you have a working example on load. Accepted range: 0–10.
Results
- Days to fully adjust
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Days with pre-trip shifting
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Pre-flight plan
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Light exposure
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the jet lag recovery time calculator work?
The body clock resets about one time zone per day, faster going west than east. This estimates recovery and a pre-flight shifting plan. The underlying maths is: Days ≈ zones ÷ 1.5 (west) or zones ÷ 1 (east)
What do I need to enter?
3 values: time zones crossed, direction, and days you can prep before flying. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the days to fully adjust result mean?
It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Estimates assume standard, average conditions — local rules, pricing, and materials vary.
Who is this tool for?
It's built for anyone doing everyday planning maths — a quick estimate that would otherwise need four browser tabs and a calculator app.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Jet Lag Recovery Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/jet-lag-recovery
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/jet-lag-recovery" target="_blank" rel="noopener">Jet Lag Recovery Calculator — RevenueLab</a> (2026).</p>
Source: [Jet Lag Recovery Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/jet-lag-recovery) (2026).