Currency exchange rates explained

A foreign-exchange rate answers a simple question: how many units of currency B equal one unit of currency A right now? In practice you will see several different “prices” for the same pair — mid-market indexes, interbank quotes, cash bureau boards, and the effective rate buried in a card statement.

Mid-market rates

The mid-market (or mid-spot) rate sits between typical bid and ask prices in wholesale markets. Apps and websites often show it because it is a fair reference. Our Pick Two Currencies and One to Many Currencies tools fetch indicative mid-style rates from an exchange-rate API when you load the page. They are not an offer to trade and not your bank’s fill price.

Spreads and fees

• Spread — the gap between buy and sell prices; how retailers earn money on FX.
• Flat fees — fixed ATM or transfer charges on top of a worse rate.
• Dynamic currency conversion (DCC) — paying in your home currency abroad; often a poor effective rate.

A mid rate of 1.27 GBP→USD can become something like 1.22–1.25 after retail markup — small percentages that matter on large sums.

How to use our converters

Pick Two when you know both currencies and an amount. One to Many when you want a glance across twenty common counterparts from one base. Convert once for a trip budget, then add a buffer for fees. For crypto assets use the crypto converters instead of ISO fiat codes.

Worked example

Budgeting £800 for a US trip at a mid rate of 1.27 suggests about $1,016 before fees. If your card applies a 2.5% FX fee, plan closer to $990 of purchasing power — or treat the mid conversion as optimistic.

Common mistakes

• Using airport cash rates as if they matched Google’s mid print.
• Accepting DCC at machines without checking the quoted rate.
• Comparing last month’s screenshot with today’s booking.

FAQs

Are weekend rates “frozen”?

Interbank markets thin out; retail spreads can widen even if an index still prints.

Is this the same as inflation?

No — spot FX is today’s exchange price. Long-run buying power uses Inflation.

Can I get historical accounting rates?

Use the rate your contract or tax authority requires; these tools are convenience checks for current indicative pricing.

Cash, cards, and transfers

Airport cash desks tend to show wide spreads because the product is convenience. Debit and credit cards often beat cash boards if your issuer’s FX fee is low and you refuse DCC. Bank transfers and specialist FX firms quote yet another price, sometimes closer to mid-market for large sums, sometimes with a wire fee that swamps savings on small top-ups. Always compute an effective rate: foreign amount received ÷ home amount spent.

Crypto is not FX

Token markets quote continuously and can gap violently. Liquidity, chain fees, and withdrawal holds differ from ISO currency rails. Use our crypto converters for coin-to-coin sketches, and keep fiat trip budgets on the currency tools so you do not mix unstable tickers into rent or ticket planning.

Sources

General FX market practice (bid/ask, mid); consumer guidance on DCC and card FX fees from major card networks’ public education materials.