Currency Converter

Where the exchange rates come from

The widget requests https://open.er-api.com/v6/latest/ followed by your source currency code, the free and key-less endpoint of the Open Exchange Rates API. The request is sent from your browser straight to that provider; this site has no server in the middle and keeps no copy of the rates. The response is a table of rates for every currency relative to the base you chose, and it is held in memory for as long as the page stays open, so changing the amount or the target currency afterwards costs no further request. Choosing a different source currency, or swapping, fetches that currency's table once.

The provider refreshes the free endpoint roughly once every 24 hours, so a rate can be almost a day old. The Rates updated line prints the time_last_update_utc value from the response, converted to a UTC label, so you can see exactly which snapshot produced your figure. If the request fails because you are offline, the provider is down or it is rate-limiting, the box reads Couldn't load exchange rates and nothing is converted; there is no stored fallback table.

How the figure is calculated

Conversion is a single multiplication: the amount times the rate for the target currency in the base table. If the USD table reports EUR at 0.92, then 250 USD becomes 250 × 0.92 = 230.00 EUR, and the line beneath shows 1 USD = 0.92 EUR, which the widget derives by dividing the result by the amount. Cross pairs such as GBP to JPY use the GBP table directly rather than going through dollars.

Rounding and small-unit currencies

• Converted amounts of one unit or more are printed with two decimals in your browser's number format; a result under one unit is shown with enough decimals for four significant digits, and the rate line keeps up to six decimals.
• For currencies with small units the extra decimals matter: 1 JPY to USD shows about 0.006700 USD rather than a rounded 0.01, and 10,000 JPY gives a plain 67.00 USD.
• Negative amounts are accepted and simply multiplied, so −50 USD returns a negative euro figure.
• Leaving the amount empty is treated as zero, so the result shows 0.00 and the rate line disappears.

The thirty currencies in the dropdowns

Exactly 30 codes are listed, most-used first. The provider's table covers many more, but only these can be selected; the message That currency pair isn't available only appears if the provider's response lacks the target code, which is rare for this list.

Mid-market rate versus the price you pay

The rates are mid-market reference values, halfway between buy and sell. A card issuer, bank or exchange bureau adds a spread of roughly 1% to 4% plus any fixed fee. On 1,000 USD at 0.92 the mid-market figure is 920 EUR; with a 3% margin you would actually receive about 892.40 EUR. Use the tool to judge whether a quoted rate is fair, not as the amount that will land in an account.

The converter has no date picker, historical rates or charts. For a rate on a past date you need a source that archives daily tables.