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.
By AdminDrafted with AI writing toolsUpdated Checked examples: 4
The trip costs about $3,630.00 ($1,815.00 each, including 10% contingency). Flying east across 5.5 hours of time difference, allow about 6 days to adjust.
In the formula, B is the budget, c_d daily spending per person, d trip days, n travellers, F fixed costs, c the contingency as a decimal fraction, z the time difference in hours and A estimated adjustment days. The average rate r is 1 hour/day eastward or 1.5 hours/day westward.
Rounded up to whole days. The CDC Yellow Book gives average adaptation of 1 hour a day flying east and 1.5 hours a day flying west; flying east that is the familiar rule of about one day per time zone.
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.
A trip budget is daily spending per person × days × travelers, plus fixed costs such as flights, with a contingency percentage added on top. Two people spending 150 a day each for 7 days, with 1,200 of fixed costs and a 10% buffer, need (2,100 + 1,200) × 1.10 = 3,630, or 1,815 each.
Spread over the week, that is 3,630 ÷ 7 = 518.57 a day for the group. It includes the fixed costs and the buffer, so it is well above the 300 a day the two travelers spend locally.
Daily spending is what one person spends in one day: lodging, meals, local transport and activities. Fixed costs are paid once for the whole group: flights, visas, insurance.
The percentage applies to the whole subtotal, fixed costs included: 10% of 3,300 is 330. If the flights are already paid, a buffer on them only inflates the total, so raise the daily rate instead to cover local spending alone.
At 165 a day (150 plus 10%) with no contingency, the same trip comes to 3,510 instead of 3,630. The 120 difference is the buffer that was sitting on the fixed costs.
The CDC Yellow Book 2026 puts average adaptation at about 1 hour of time difference per day flying east and 1.5 hours per day flying west. Divide the time difference by that rate and round up to whole days.
London to Delhi in winter is 5.5 hours east: 5.5 ÷ 1 = 5.5, so about 6 days. Flying home west, 5.5 ÷ 1.5 = 3.67, so about 4 days. Use the clock difference in hours; half-hour offsets such as India's are fine.
The same rule for other time differences:
These are averages for planning, not a forecast for one traveler. The CDC describes jet lag disorder after crossing at least two time zones, so a 1-hour change is usually minor.
Beyond 12 hours of difference, the body clock may adjust the other way around the globe, so treat those estimates loosely.
| Scenario | Total budget | Per person | Adjustment days |
|---|---|---|---|
| Default | 3630.000000 | 1815.000000 | 6.000000 |
| Westbound | 3630.000000 | 1815.000000 | 4.000000 |
| No time change | 3300.000000 | 1650.000000 | 0.000000 |
| Fixed only | 900.000000 | 300.000000 | 6.000000 |
| Solo weekend | 299.000000 | 299.000000 | 0.000000 |
The expense splitter works out who owes whom from the actual receipts. For a road trip, the fuel cost calculator estimates the fuel to add to fixed costs.
Checked against: (150×7×2 + 1200) × 1.10 = 3630; ceil(5.5 / 1) = 6 (CDC eastward rate)
Checked against: ceil(5.5 / 1.5) = ceil(3.67) = 4 (CDC westward rate)
Checked against: Hand calculation: 2100 + 1200; 0 zones need no adjustment
Checked against: 9 / 1.5 = 6 days (CDC westward rate)
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.
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.
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. The CDC notes that 0.5 to 1 mg of melatonin is often enough to shift the body clock, but taking it at the wrong time can worsen misalignment. Ask a clinician or pharmacist about its use and timing for your circumstances. For trips of less than 2 days it advises staying on home time.
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).
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.
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