The standard approach — find a daily budget figure online, multiply by the number of days — fails for two reasons. Costs vary by a factor of five between regions, so an average across a multi-country trip describes nowhere. And a large share of what a trip costs is not daily at all.
A budget that holds up separates the two.
Fixed costs, which happen whether or not you leave the room
Work these out first, in full, before thinking about daily spending. For a long trip they are frequently a third of the total.
Flights, including the intercontinental legs and any internal ones you already know you need.
Insurance for the full duration. A year of decent long-stay cover is a real number.
Visas and travel authorisations for every country, which for a multi-country trip adds up faster than people expect.
Vaccinations, which are not always free and can run into the hundreds for a full course including rabies and Japanese encephalitis.
Equipment you do not already own — a bag, boots, a sleeping bag, a jacket for altitude.
The set pieces. This is the category that wrecks budgets. Antarctica, a Galápagos cruise, a gorilla permit, the Inca Trail, a diving certification, a safari — any one of these can cost more than a month of ordinary travel. Decide which you are doing and put them in the fixed column, not the daily one.
Costs at home that continue: rent or mortgage, storage, insurance, phone, subscriptions, tax. People forget these constantly and they are often the largest number on the page.
Daily costs, by region
Then estimate daily spending in bands rather than a single figure.
Very cheap — South Asia, Southeast Asia outside Singapore, Bolivia, Egypt, the Balkans, Georgia, Central America’s northern half.
Moderate — Turkey, Morocco, Mexico, Peru, southern and eastern Europe, South Africa, Japan, Korea, Malaysia.
Expensive — western and northern Europe, Australia, New Zealand, Chile, Costa Rica, the Gulf, Iceland, Botswana.
Within any of those, your own daily figure depends far more on how you sleep and drink than on the country. A dorm bed and street food in an expensive country can cost less than a private room and restaurants in a cheap one.
The four levers, in order of size
Accommodation is the largest and the most controllable. A dorm, a private guesthouse room and a mid-range hotel in the same city can be a factor of six apart. The weekly or monthly rate, which is almost never advertised, is routinely 30 to 50 per cent below the nightly one — see the accommodation guide.
Movement is the second. Every journey costs money and a day. Going slower is the single most effective budget measure available, and it improves the trip rather than degrading it.
Alcohol is the third and the one people underestimate hardest. In much of Europe, Australia and the Gulf, drinks can exceed food. Cutting from every night to three nights a week transforms a budget without transforming the trip.
Eating out for every meal is the fourth. Cooking two or three times a week is enough to matter, which requires accommodation with a kitchen, which requires staying more than two nights.
Contingency
At least 15 per cent, and 20 for a trip over three months.
What it is for, based on what actually happens: a flight rebooked after a missed connection; a week of being ill, which means paying for a room and not moving; a stolen phone; a dental problem; a family emergency at home requiring an immediate flight; and the thing you had not heard of that turns out to be unmissable.
A trip without contingency ends early. That is the whole argument.
Tracking, lightly
Weekly, not daily. Daily tracking punishes the day you took an expensive bus and rewards the day you did nothing, which is exactly backwards.
A spreadsheet or one of the split-and-track apps, updated once a week, is enough to catch a drift before it becomes a problem.
Watch the trend, not the number. Being 10 per cent over in week one means nothing. Being 10 per cent over every week for six weeks means the trip is three weeks shorter than planned, and that is worth knowing in month two rather than month five.
The two decisions worth making in advance
What you will not economise on. For most people: safety, and sleep before a long journey. Writing it down means you do not have the argument with yourself at 11pm at a bus station.
What the trip is for. If it is diving, budget for diving and eat cheaply. If it is food, budget for food and sleep in dorms. A budget spread evenly across everything produces a trip that is adequate at all of it and good at none.