Take four friends on a two-week trip in Europe, with expenses in euros (France), pounds (UK), and Swiss francs (Switzerland), plus some pre-trip bookings in US dollars. By the end, it can be hard to tell who owes what in which currency, and the exchange rates have shifted since the trip started.
The Core Problem: Which Rate Do You Use?
Suppose Sarah pays €200 for a hotel in Paris and Mike needs to pay her back in dollars. The key question is: which exchange rate applies?
- The rate when Sarah paid? (What she actually spent)
- The rate when Mike pays her back? (What Mike actually sends)
- The "average" rate during the trip?
A simple and fair rule: use the rate at the time of the expense. If the rate was $1.08/€ when Sarah paid (an illustrative rate), the €200 expense is recorded as $216. Everyone's share is calculated in the group's "home currency." This eliminates the ambiguity of floating rates.
Single-Currency Accounting
The easiest approach for multi-currency trips: pick one settlement currency (usually the group's home currency) and convert everything to that currency at the time of entry. If your group is American, all expenses — whether paid in euros, pounds, or francs — are recorded in USD using the day's exchange rate.
This means the settlement at the end is entirely in one currency. A single figure such as "Mike owes Sarah $143" is much cleaner than "Mike owes Sarah €87 and £22" (example amounts).
Credit Card Rates vs. Cash Rates
When someone pays with a credit card abroad, their card issuer may apply its own exchange rate and a foreign transaction fee. When someone pays cash, they got that cash from an ATM or exchange booth at yet another rate.
For expense-splitting purposes, use the amount that appears on the receipt in local currency and convert using a neutral source (such as Google or XE.com) at the day's mid-market rate. Don't try to account for individual credit card fees — that level of precision can create more arguments than it resolves.
The Pre-Trip Booking Problem
Flights, Airbnbs, and rail passes are often booked weeks or months before the trip. The exchange rate at booking might be very different from the rate during the trip. Rule of thumb: record pre-trip expenses at the rate they were actually charged. For example, if Sarah booked the Airbnb at $1.12/€ in March, that's the rate for that expense, even if the rate is $1.08 when the trip happens in June (again, illustrative rates).
Keeping Track of Several Currencies
Manually converting every expense across three currencies with a calculator is error-prone. A spreadsheet that records each expense with its currency and the day's rate can do the conversion for you. Another option is a tool that supports multiple currencies: enter each expense in the currency it was paid, and let the tool handle the conversion and net-balance calculation.