Every time you swipe a card abroad or send money across a border, two prices exist: the rate banks trade at, and the rate you actually get. The gap between them is where currency conversion gets expensive — and confusing. This guide walks through the moving parts so you can read any quote critically.
The Building Blocks of an Exchange Rate
| Term | What It Means | Typical Range |
|---|---|---|
| Mid-market rate | True interbank midpoint | What Google shows |
| Bid | What a dealer will pay you | Below mid |
| Ask | What a dealer charges you | Above mid |
| Spread | Ask minus bid, as % of mid | 0.1%–3% |
| Markup | Provider's hidden margin | 0.5%–5% |
| Pip | Smallest standard move | 0.0001 for most pairs |
Mid-Market vs Retail
The interbank market deals in millions of units, and major pairs trade with razor-thin spreads. Retail customers move smaller amounts and are charged for the convenience. A retail provider quoting EUR/USD might use a mid of 1.0850 but show you 1.0800 to buy euros — that is a 0.46% markup baked into the rate, on top of any visible fee.
Card networks (Visa, Mastercard) and travel cards usually publish their daily rate openly, often within 0.2–0.5% of mid-market. Your bank may then add its own foreign-transaction fee of 1–3%. Cash exchanges at airports are the worst case — spreads of 5–10% are common.
Spotting the Real Cost
- Look up the mid-market rate on a neutral source like Google or XE.
- Get the quote for the exact amount you want to convert, including all fees.
- Divide the amount received by the amount sent and compare to mid.
- Whatever percentage gap you see is your total cost, no matter how the provider labels it.
Worked Example: £1,000 to Euros
Say the mid-market rate is GBP/EUR 1.1700, so £1,000 is €1,170 in a perfect world. Compare three realistic offers:
- “Zero-fee” bureau quoting 1.1300: you receive €1,130. The hidden cost is €40 — a 3.4% spread disguised as “no fees.”
- Bank transfer at 1.1550 plus a £15 flat fee: €1,138 effective on £1,000, about a 2.7% total cost.
- Mid-market app at 1.1690 plus a 0.4% fee: roughly €1,165, a 0.4% total cost.
All three advertise differently, but the only honest comparison is euros-in-hand divided by pounds-sent. Run that one division and the cheapest option is obvious, regardless of how the marketing is worded.
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