How to track expenses in multiple currencies without the numbers drifting
If you earn in one currency and spend in another, or keep savings abroad, a single list of transactions quickly stops making sense. The fix is structural, not mathematical.
Who needs multi-currency tracking
Freelancers paid in US dollars who spend in their local currency. People living abroad with an account back home. Anyone who travels, or who keeps savings in a stronger currency. In all of these cases, amounts in different currencies end up side by side — and adding them together as if they were the same is how totals go wrong.
Rule 1: one wallet per currency
Every account or pocket of money should live in exactly one currency, and every transaction in it should be recorded in that currency — the amount you actually paid, as it appears on the receipt or statement. A USD account records dollars; a cash wallet in pesos records pesos. Never record a converted amount in place of the real one: the real amount is what lets your balance match your statement.
Rule 2: never let a wallet's currency change
If a wallet's currency can be switched later, every old transaction in it silently changes meaning. Pick the currency when you create the wallet and treat it as permanent. If you open a new account in a new currency, give it a new wallet.
Rule 3: convert only for the overview
You still want one number that answers "how much do I have in total?". That is a reporting question, and it is the only place conversion belongs. Choose one base currency — usually the one you think in — and convert every wallet into it for the overview, using a current exchange rate. The underlying transactions stay untouched in their own currency.
Rule 4: budget inside one currency
A budget that mixes currencies moves with exchange rates, not with your spending. Keep each budget scoped to a single wallet, in that wallet's currency, so progress reflects what you spent.
A worked example
Sara is paid in USD and lives in a country that uses another currency. She keeps a USD wallet for her salary and savings, and a local-currency wallet for day-to-day spending. Groceries go into the local wallet in local currency; her salary goes into the USD wallet in dollars. Her dashboard converts both into her base currency, so she sees one total — while each wallet on its own still shows its real balance.
Doing this in Coinly
Coinly works exactly this way. Each wallet's currency is chosen once and locked forever, so it never gets mixed up with old transactions or budgets. The "All Wallets" view converts everything into your Base Currency using daily-refreshed rates cached on your device; open a single wallet and it stays in its own currency, unconverted. Budgets are always scoped to one wallet. Coinly supports 166 currencies; wallets in more than one currency are part of Coinly Pro.