Where the rates come from and how conversion works
When you pick the currency to convert from, the page requests that currency as the base from this site's own /api/rates endpoint. The endpoint fetches a table of rates from the open.er-api.com service and caches it for about an hour. The table lists how many units of every other currency one unit of the base buys. Converting is a single multiplication:
converted = amount × rate(to)
The rates are updated by the provider roughly once a day, and the page shows the timestamp of the last update. They are daily reference rates, not a live trading feed, so they will not track intraday moves.
Worked example
Suppose the provider lists 1 USD = 0.92 EUR (an illustrative rate, not a quote). Then:
- 500 USD × 0.92 = 460.00 EUR
- Swapping the pair reloads the table with EUR as the base, so 1 EUR = about 1.087 USD, because 1 ÷ 0.92 is about 1.087
- The mini table underneath multiplies the same amount by the USD, EUR, GBP, JPY, INR, CAD, AUD and CHF rates, so you can compare several destinations at once
Mid-market rate versus the rate you actually get
The figure shown is a mid-market rate, roughly the midpoint between what banks buy and sell a currency at. Consumers rarely get it. A card issuer, bank or airport kiosk usually adds a margin or fee, and the final difference is often a few percent. The practical way to compare options is to calculate the effective rate yourself: divide what you received by what you sent, then compare it with the mid-market rate.
| You send | Provider delivers | Effective rate | Cost versus 0.92 mid-market |
|---|---|---|---|
| 1,000 USD | 900 EUR | 0.900 | about 2.2% worse |
| 1,000 USD | 880 EUR | 0.880 | about 4.3% worse |
| 1,000 USD | 915 EUR | 0.915 | about 0.5% worse |
Common mistakes
- Treating a rate as final. Rates move daily, and for large transfers a one-day move of 1% is real money.
- Forgetting fees. Flat transfer fees, ATM charges and dynamic currency conversion at checkout (choosing to pay in your home currency abroad) are all separate from the rate.
- Reading the direction backwards. A rate of 0.92 for USD to EUR means 1 USD buys 0.92 EUR, not the other way around.
- Zero-decimal currencies. Currencies like JPY and KRW have no minor unit in everyday use, so conversions produce large numbers and the rounding differs from dollars and euros.
The guide how exchange rates work explains why they move. To convert measurements instead of money use the unit converter, and to work out discounts or margins use the percentage calculator.