How exchange rates work (and why the rate you get is different)
You look up "1 USD to EUR," get a clean number, then your bank hands you noticeably less. Exchange rates are simple in theory and full of hidden costs in practice. Here's what's going on.
What an exchange rate is
An exchange rate is simply how much of one currency you need to buy one unit of another. If EUR/USD is 1.08, one euro costs 1.08 dollars. Rates move constantly — by the second during market hours — driven by interest rates, inflation, trade, and demand for each currency.
The "mid-market" rate vs. what you actually get
The rate you see on Google or a finance site is the mid-market rate — the midpoint between what buyers and sellers are quoting. It's the "real" rate, but it's not what a bank or exchange booth gives you. They add a margin (spread) and often a fee:
- Spread: they buy at one rate and sell to you at a worse one, keeping the difference.
- Fees: a flat charge or percentage on top.
- Airport/hotel booths have the worst rates of all — convenience is expensive.
The mid-market rate is your benchmark. If a provider is close to it, that's a good deal; the further from it, the more you're paying.
How cross-rates work
Not every currency pair is quoted directly. To convert, say, Korean won to Mexican pesos, systems often go through a common currency like the US dollar: won → dollars → pesos. That's why a good converter uses a live base rate and derives every pair from it.
Converting accurately
For a real-time figure, use a converter that pulls live mid-market rates, then remember to mentally add a few percent for whatever your bank or card will actually charge. For travel, comparing your card's foreign-transaction fee against cash exchange is worth doing before you go.