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Live daily exchange rates for every major currency.
A currency converter turns an amount in one currency into another using the exchange rate, the price of one currency in terms of another, which moves constantly as markets trade. The rate you see quoted here and in the news is the mid-market rate, the midpoint between what buyers and sellers are offering. It is the fairest reference point and the number to check a deal against, but it is usually not the exact rate you personally get when you spend or transfer money.
Why the rate you pay is worse. Banks, card networks and bureaux add a margin to the mid-market rate, and often a fee on top, which is how they make money on the exchange. That margin can be small on a good travel card or large at an airport kiosk, so two providers converting the same amount can hand you noticeably different totals. Always compare the rate you are offered against the mid-market rate above to see the real markup you are paying.
Practical tips. When a card machine abroad offers to charge you in your home currency ("dynamic currency conversion"), decline it and pay in the local currency, as the home-currency option bakes in a poor rate. For larger transfers, a dedicated money-transfer service usually beats a high-street bank. And remember rates move daily, so a quote is a snapshot, not a promise.