The formula
total = fixed + (daily spend × people × days) + nightly rate × nights + buffer
Where it comes from
A trip has three kinds of spending that behave differently, and mixing them is why the numbers never add up. The fixed ones — return travel, insurance, visas — do not change if you stay an extra day. The daily per-person ones — food, local transport, entrance fees — are multiplied by both. And accommodation is per night and per room, which is one fewer than the days and is not multiplied by the travellers. Separating them shows at a glance which lever actually moves the budget.
How to work it out by hand
- Add up the fixed costs of the trip
- Add the daily spend per person and multiply by the days and by the people
- Count the nights, which are the days minus one, and multiply by the nightly rate
- Add a percentage buffer on top of everything above
What is worth knowing
The buffer for the unexpected is not optional: ten to fifteen per cent covers an unfavourable exchange rate, the excursion that turns out dearer than planned and the taxi on the last night. The figure for what one extra day costs is usually the most useful of all, because a trip gets longer or shorter far more easily than it changes destination, and one glance tells you whether it is worth it. Nights are days minus one: it is the most repeated mistake in budgeting a trip.