# Travel budget and jet lag calculator

> Trip budget from daily spending per person, fixed costs and a contingency, plus how many days of jet lag to expect after crossing time zones.

Interactive version: https://www.calcopenly.com/everyday/travel-budget-and-jet-lag-calculator
Subject: Everyday calculators

The trip budget is daily spending per person × days × travellers, plus fixed costs such as flights and visas, with a contingency percentage added on top of both. The jet lag estimate divides the time difference by how fast the body clock adapts, which the CDC Yellow Book 2026 puts at about 1 hour a day flying east and 1.5 hours a day flying west, and rounds up to whole days.

With the defaults, two travellers spending 150 a day each for 7 days, with 1,200 of fixed costs and a 10% contingency, need 3,630 in total, or 1,815 each. Flying east across 5.5 hours of time difference takes about 6 days to adjust; flying west, 4.

The adaptation rates are averages, and the CDC describes jet lag disorder only after crossing at least two time zones. Days to adjust are rounded up, and the timeline marks the day of the trip when your body clock should match local time.

## Inputs

- **Trip length**
- **Travellers**
- **Daily spending per person**: Lodging, food, local transport and activities.
- **Fixed costs for the group**: Flights, visas, insurance and anything else paid once.
- **Contingency**
- **Time zones crossed**: The time difference in hours; half-hour zones are fine.
- **Flying** (options: East, West)

## Results

- Trip budget — main result
- Per person
- Per day for the group
- Daily spending over the trip
- Contingency
- Days to adjust to local time (days)

## Formula

$$
\begin{gathered}\text{budget} = (\text{daily} \times \text{days} \times \text{people} + \text{fixed})(1 + c) \\ \text{adjust days} = \left\lceil \frac{\text{zones}}{r} \right\rceil,\quad r = 1\ \text{h/day east},\ 1.5\ \text{h/day west}\end{gathered}
$$

## Worked examples

### A week for two, 5½ zones east

- Trip length: 7 days
- Travellers: 2
- Daily spending per person: 150
- Fixed costs for the group: 1200
- Contingency: 10%
- Time zones crossed: 5.5 hours
- Flying: East
- **Daily spending over the trip: 2,100.00**
- **Contingency: 330.00**
- **Trip budget: 3,630.00**
- **Per person: 1,815.00**
- **Per day for the group: 518.57**
- **Days to adjust to local time: 6 days**
- Checked against: Python decimal: (150×7×2 + 1200) × 1.10 = 3630; ceil(5.5 / 1) = 6 (CDC eastward rate)

### Same trip flying west

- Trip length: 7 days
- Travellers: 2
- Daily spending per person: 150
- Fixed costs for the group: 1200
- Contingency: 10%
- Time zones crossed: 5.5 hours
- Flying: West
- **Days to adjust to local time: 4 days**
- Checked against: Python decimal: ceil(5.5 / 1.5) = ceil(3.67) = 4 (CDC westward rate)

### No time change and no contingency

- Trip length: 7 days
- Travellers: 2
- Daily spending per person: 150
- Fixed costs for the group: 1200
- Contingency: 0%
- Time zones crossed: 0 hours
- Flying: East
- **Trip budget: 3,300.00**
- **Days to adjust to local time: 0 days**
- Checked against: Hand calculation: 2100 + 1200; 0 zones need no adjustment

### Nine zones west

- Trip length: 7 days
- Travellers: 2
- Daily spending per person: 150
- Fixed costs for the group: 1200
- Contingency: 10%
- Time zones crossed: 9 hours
- Flying: West
- **Days to adjust to local time: 6 days**
- Checked against: 9 / 1.5 = 6 days (CDC westward rate)

## Questions

### How long does jet lag last?

About one day per time zone flying east and two days for every three zones flying west. The CDC Yellow Book 2026 gives average body-clock adaptation of 1 hour a day eastward and 1.5 hours a day westward, so 6 hours of time difference takes about 6 days east and 4 days west. Symptoms include poor sleep, daytime sleepiness, impaired thinking, general malaise and stomach upset.

### Why is jet lag worse flying east?

Flying east means advancing the body clock, and because the natural circadian rhythm runs slightly longer than 24 hours, it is easier to delay than to advance. The CDC Yellow Book 2026 therefore gives adaptation of 1 hour a day eastward against 1.5 hours a day westward. For 9 hours of time difference that is about 9 days flying east and 6 days flying west.

### How can you reduce jet lag?

The CDC Yellow Book 2026 suggests shifting sleep 1 hour a day for the 2 to 3 days before departure (earlier before flying east, later before flying west), timing meals, sleep and light to the destination during the flight, getting natural light on arrival and avoiding long daytime naps. Low-dose melatonin of 0.5 to 1 mg is often enough to shift the body clock. For trips of less than 2 days it advises staying on home time.

### Does a one- or two-hour time change cause jet lag?

Usually not much. The CDC Yellow Book defines jet lag disorder as occurring after crossing at least two time zones, so a 1-hour change, like a daylight saving time shift, is usually minor. At 2 hours the calculator estimates 2 days to adjust flying east (2 ÷ 1) and 2 days flying west (2 ÷ 1.5 = 1.33, rounded up).

### How do you work out a daily travel budget?

Add up lodging, food, local transport and activities for one person for one day, then multiply by days and travellers. Costs paid once, such as flights, visas and insurance, go in fixed costs. A 10% contingency on a 3,300 trip adds 330. Per day for the group divides the whole total, flights included, by the trip length: 3,630 ÷ 7 = 518.57.

### How accurate is the travel budget and jet lag calculator?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 4 worked examples whose answers come from independent sources; for example, “A week for two, 5½ zones east” is checked against Python decimal: (150×7×2 + 1200) × 1.10 = 3630; ceil(5.5 / 1) = 6 (CDC eastward rate).

### Where does the method come from?

CDC Yellow Book 2026 — Jet lag disorder (adaptation ~1 h/day eastward, ~1.5 h/day westward).

## Sources

- [CDC Yellow Book 2026 — Jet lag disorder (adaptation ~1 h/day eastward, ~1.5 h/day westward)](https://www.cdc.gov/yellow-book/hcp/travel-air-sea/jet-lag-disorder.html)