It converts an amount from one currency to another using mid-market exchange rates, and shows the rate both ways, for example "1 USD = 25,897.06 VND" and "1 VND = 0.0000386144 USD". A table below gives the same amount in every other currency. There are 32 currencies: the US dollar, euro, Vietnamese dong, Japanese yen, Korean won, pound sterling, Chinese yuan, Thai baht, Singapore and Australian dollars, and twenty-two more used across Asia, Europe and the Americas. Results are rounded to each currency's usual number of decimals: none for the dong, yen and won, two for most others.
Where the rates come from
This is the one tool on the site that makes a network request, and it is worth being precise about it. When the page opens, your browser downloads a public table of exchange rates against the US dollar from open.er-api.com, the free service of ExchangeRate-API. The request is identical for every visitor: it contains no amount, no currency you picked and nothing you type, and the conversion itself happens on your device. Like any web server, that service sees your IP address and the time of the request. The table is kept in memory for an hour, so changing currencies does not ask again.
The provider updates its table about once a day, and the tool shows the update time in UTC. If the request fails, for example when you are offline or a network blocks it, the tool says so and uses a copy of the rates saved with the page (from 12 October 2026, 23:57 UTC), with a Try again button.
Every currency is converted through the US dollar. To turn euros into dong, the tool divides by the euro's rate and multiplies by the dong's: with the saved table, 25,897.062624 ÷ 0.895156 gives 1 EUR = 28,930.22 VND. The rates are used as exact decimals and rounded once at the end, so 100 USD becomes exactly 2,589,706 VND and 1,000,000 VND becomes 38.61 USD with that table.
Why your bank's rate is different
The rates here are mid-market rates: halfway between what buyers pay and sellers ask in the wholesale market. Nobody hands you cash at that rate. A bank or exchange counter quotes two prices, a lower one at which it buys foreign money from you and a higher one at which it sells to you, and the gap (the spread) is its margin. Card payments abroad are converted at the card network's rate, and many banks add a foreign transaction fee of a few per cent on top. Use this converter to know what an amount is roughly worth and to judge how much margin an offer includes; the post on how exchange rates and spreads work shows how to work out that margin.
