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Circadian Rhythm Shift Calculator

Work out circadian rhythm shift instantly with clear inputs, formula shown and shareable results.

About Circadian Rhythm Shift Calculator

Estimates jet lag adaptation time from the number of time zones crossed, allowing for the faster phase delay achieved when travelling westward.

Formula

Circadian adaptation

Days to adapt = time zones crossed / achievable shift per day, with westward delays typically achieved about 1.5 times faster than eastward advances

Worked example

With the default values below, Circadian Rhythm Shift Calculator returns Estimated days to adapt of 6.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Time zones crossedaccepts 1–14
6
Direction of travelone of Eastward (phase advance), Westward (phase delay)
Eastward (phase advance)
Achievable shift per dayaccepts 0.5–2 h/day
1 h/day

Results

Estimated days to adapt
6.0 days
Required phase shift
6 h
Direction effect
Eastward travel needs a phase advance, which the body clock resists
Assumed shift achieved
1.00 h/day

Step by step

  1. 1Values used
  2. 2Circadian adaptation
  3. 3Estimated days to adapt= 6.0 days
  4. 4Required phase shift= 6 h
  5. 5Direction effect= Eastward travel needs a phase advance, which the body clock resists
  6. 6Assumed shift achieved= 1.00 h/day

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Why is eastward travel harder?

The free-running human circadian period is slightly longer than 24 hours, so delaying the clock is easier than advancing it.

Can adaptation be accelerated?

Timed light exposure, meal timing and melatonin can speed realignment, though the direction of the shift still matters.

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