Where the exchange rates come from

Roampurse converts with official reference rates that two central banks publish free of charge. It doesn’t change them, and every conversion tells you which source it used and from which day.

The sources

When a currency appears in more than one table, Roampurse uses the ECB first, then NBP table A, then table B. The euro is the base for ECB rates and the Polish złoty for NBP rates; to cross them, the app uses the US dollar and the euro from the same table and the same date, so two days are never mixed in one rate.

A few currencies are fixed by law to another one. Roampurse uses those pegs only where it can cite the official source: the Bhutanese ngultrum (BTN) at par with the Indian rupee, the Falkland Islands and Saint Helena pounds (FKP, SHP) at par with the pound sterling, the Bermudian dollar (BMD) at par with the US dollar, and the Cayman Islands dollar (KYD) at 1.20 US dollars. That brings coverage to 153 of the 155 currencies in circulation. For the other two, the North Korean won (KPW) and Venezuela’s VED, there is no reference rate we can cite, so you enter your own.

Your rate is frozen with the expense

Each expense stores the rate it was converted with, its source and its date. When new rates arrive, nothing you already added moves. Your total for last Tuesday’s dinner stays what it was on Tuesday.

If you add expenses with no connection, they use the latest rate on your phone and are marked “Added offline”. When the rates for those days arrive, Roampurse asks once whether to use each day’s own rate. It never changes them without asking.

When to use your own rate

A reference rate is the middle of the market. What you actually pay is usually a little worse: the exchange booth keeps a margin, your card adds a fee, an ATM may offer its own conversion. If you want your totals to match your bank, enter the rate you really got, fees included.

• For one expense: tap the rate line under the amount and choose “Your rate for this expense”. You can type it either way round (1 US$ = … ฿ or 1 ฿ = … US$), whichever your receipt uses.
• For the whole trip: set your rate for a currency, and Roampurse asks whether to apply it to the expenses you already added too.
• For your cash: log “I changed money” (“I got 5,000 ฿, it cost me US$…”) and Roampurse works out your real rate and suggests it for everything you pay with that cash.

Your own rate is free, like the reference rates.

Currencies with a street rate

In some countries the official rate and the rate people actually get are far apart. On 23 September 2026 we compared NBP’s weekly table with a commercial rate feed. Most currencies were within 1 %; three were not:

The first time you pick one of these currencies on a trip, Roampurse tells you, shows the official rate with its source and date, and suggests entering the rate you were given. If you keep the official one, a small amber mark stays next to those amounts so you remember. Other currencies are sometimes said to have a parallel rate too, but we found no source we could cite for 2025–26, so there’s no automatic warning; your own rate works exactly the same way for them.

Old rates are never silent

The date of the rate is always next to the conversion. If your rates are more than 7 days old (14 for the weekly table), the date turns amber and a note on the Today screen says so. They update on their own as soon as you’re online, at most once a day, straight from the ECB and NBP websites. Roampurse has no server of its own in between.

What reference rates are not

Citing the sources

The rates are published free by the European Central Bank and the National Bank of Poland. Roampurse shows the source next to every rate (“Source: ECB”, “Source: NBP”) and doesn’t alter the figures. Settings › Exchange rates lists the source and date of each currency.

Counts of currencies read from the tables published on 2026-09-29 (ECB, NBP table A) and 2026-09-23 (NBP table B).