Buy and sell exchange rates differ because currency is quoted as a two-way price: a lower bid, at which the market buys a currency from you, and a higher offer, at which it sells one to you. The gap between the two is the bid-offer spread. On heavily traded pairs it is very small — on a large transfer, the margin your provider adds to the rate is almost always the far larger cost.
Understanding the difference between the spread and the margin is what lets you read a quote properly and see where the real cost of a transfer sits. This guide explains how a rate is quoted, why there are two prices, and how much the spread actually costs when you move a serious sum.
What is the bid-offer spread on an exchange rate?
The bid-offer spread is the difference between the price at which the market will buy a currency and the price at which it will sell the same currency at that moment. The bid is always the lower number and the offer (also called the ask) is the higher one. The spread is the gap between them.
Every tradeable market works this way, from shares to gold. In foreign exchange the spread is usually quoted in tiny increments called pips — the fourth decimal place of most rates. If GBP/EUR is shown as 1.1699 / 1.1701, the bid is 1.1699, the offer is 1.1701, and the spread is two pips. You buy euros at the offer and sell them back at the bid, so the two-way price is why a “buy” rate and a “sell” rate are never identical.
This is different from the single mid-market rate you see on a currency converter. The mid-market rate is simply the midpoint between the bid and the offer — a reference number, not a price anyone actually deals at.
Why are there two prices — a bid and an offer?
The two-way price exists because the party quoting it is taking on risk and providing immediacy. When a bank or broker quotes you a rate, it is offering to trade right now, in the size you want, and to take the opposite side of your deal. It then has to manage the currency it has bought or sold until it can offset the position.
The spread is the compensation for that service and that risk. It is effectively the price of being able to transact instantly rather than waiting to find someone who wants the exact opposite trade. In a deep, fast-moving market this cost is minimal; in a thin or nervous one it widens, because the risk of holding the position is greater.
Foreign exchange is a decentralised, over-the-counter market with no single exchange, trading around the clock on weekdays. In April 2025 it turned over about US$9.6 trillion a day, according to the Bank for International Settlements, and the United Kingdom is the largest centre for that trading. That depth is exactly why spreads on the main pairs are so tight.
What do “base currency” and “quote currency” mean?
In any currency pair, the first currency is the base and the second is the quote (or counter) currency. The rate tells you how many units of the quote currency it takes to buy one unit of the base. In GBP/EUR, the pound is the base and the euro is the quote, so a rate of 1.17 means one pound buys 1.17 euros.
Reading the pair the right way round matters when you are budgeting a transfer. If you are converting pounds into euros to buy a property in Spain, a higher GBP/EUR number is better for you — each pound buys more euros. If you are bringing euros back to sterling, the opposite is true. The same logic applies to what a pound buys in US dollars or any other pair. For the mechanics of converting an amount once you have a rate, see our guide on how to calculate an exchange rate.
Is the bid-offer spread the same as the margin I pay?
No — and this is the distinction that matters most. The bid-offer spread is set by the wholesale market and reflects liquidity. The margin is what your provider adds on top of the wholesale rate to price your deal. When you compare a quote against the mid-market rate, most of the difference you see is the margin, not the market spread.
This is why a headline claim of “no commission” or “zero fees” can be misleading. A provider can charge nothing in explicit fees and still build its entire cost into the exchange rate as margin. The rate you are quoted already contains it. Separating the four components below shows where your money actually goes.
| Component of the rate | What it is | Who sets it | Typical size on a major pair |
|---|---|---|---|
| Mid-market (reference) rate | The midpoint between the wholesale bid and offer | The global market | The benchmark — nobody deals exactly here |
| Bid-offer (market) spread | The wholesale gap between buying and selling | Market liquidity and volatility | A fraction of a percent on major pairs |
| Provider margin | The mark-up added to the wholesale rate | Your bank or broker | Usually the largest single cost |
| Transfer or handling fee | A separate flat or percentage charge, if any | Your provider | Zero to a fixed amount per transfer |
Why is the spread wider on some currencies than others?
Spreads track liquidity. The more a currency is traded, the tighter the gap between its bid and offer, because there is always another buyer or seller close by. The US dollar sits on one side of the large majority of all trades, and the most heavily traded pairs — such as EUR/USD and GBP/USD — are where the market is deepest, so their spreads are the narrowest.
Less-traded and emerging-market currencies carry wider spreads. There are fewer participants, positions are harder to offset, and the risk of holding them is greater, so the two-way price is naturally further apart. A wide spread on an exotic currency is usually genuine illiquidity rather than a provider overcharging.
Spreads also move with conditions. They widen around major economic releases, central-bank decisions and outside the busiest trading hours, when fewer participants are active. This is separate from the trend itself — for how the time you deal interacts with the rate, see our guide on the best time to exchange currency, and browse live rates across more than 100 pairs to see how much tighter the majors trade.
How much does the bid-offer spread cost on a large transfer?
On a major pair, far less than most people expect — and far less than the margin. A worked example makes the scale clear.
Suppose you are converting £400,000 into euros, and the mid-market rate is an illustrative 1.1700. At the mid, £400,000 would buy €468,000. If the wholesale two-way spread is two pips, crossing it costs roughly €80 — a rounding error on a transfer this size.
Now apply an illustrative provider margin of 2%. That moves your dealt rate to about 1.1466, so £400,000 buys €458,640 — around €9,360 less than the mid. On this illustration the margin costs roughly 117 times as much as the market spread. The lesson is simple: the buy-versus-sell gap you notice first is trivial, while the margin baked into the rate is where a large transfer is won or lost.
Because the margin is proportional to the amount but the cost of handling a deal is largely fixed, larger transfers can attract a tighter margin — the reason a specialist can often quote a sharper rate on serious sums. That is covered in detail in our guide on whether you can negotiate a better exchange rate on a large transfer, and in our wider comparison of banks, brokers and apps.
Common mistakes people make with buy and sell rates
- Assuming the whole gap from the mid is “the spread”. Most of the difference between a quote and the mid-market rate is the provider’s margin, not the wholesale bid-offer spread.
- Trusting a “0% commission” headline. A provider can charge no explicit fee and still recover its cost inside the exchange rate. Always compare the dealt rate to the mid at the same moment.
- Reading the pair the wrong way round. Confusing the buy side and the sell side when budgeting can flip whether a rate move helps or hurts you.
- Treating a wide exotic-currency spread as a rip-off. For thinly traded currencies, a wider two-way price reflects real market illiquidity.
- Fixating on the tiny buy-sell gap while ignoring the trend. A few pips of spread are dwarfed by a multi-week move in the rate — the bigger variable to plan around.
How a specialist broker quotes a large transfer
A specialist currency broker prices from the same wholesale market as a bank, then adds its own margin. The difference clients notice is transparency: the margin is disclosed on the call, so you can see the dealt rate against the mid-market reference and know exactly what you are paying. Cambridge Currencies offers competitive rates compared with high-street banks, with every transaction completed by phone with a dedicated specialist rather than through an app.
Cambridge Currencies operates with FCA-authorised payment partners Currencycloud (FRN 900199) and ScioPay (FRN 927951), and client money is held in safeguarded accounts. You can read more about how funds are safeguarded before any transfer is made.
Frequently asked questions
Is a smaller bid-offer spread always a better deal?
Not necessarily. The bid-offer spread on a major pair is tiny, so the size of the provider margin usually matters far more to your final cost. A quote with an advertised “tight spread” but a wide margin can be more expensive than one presented differently. Compare the dealt rate against the mid-market rate at the same moment to see the true cost.
What is the mid-market rate, and can I trade at it?
The mid-market rate is the midpoint between the wholesale bid and offer. It is the reference figure quoted on financial sites and published rates such as the European Central Bank’s euro reference exchange rates. It is a benchmark, not a dealable price — no provider trades at the exact mid, because the spread and any margin sit around it. Use it as your yardstick, then measure a live quote against it.
Why is the rate for holiday cash so much worse?
Bureaux de change and airport kiosks apply a much wider margin than a broker handling a large electronic transfer, and they deal in small amounts where fixed handling costs weigh heavily. The physical-cash rate you see on a high-street board is not comparable to the rate available on a bank-to-bank transfer of a substantial sum.
Does the spread change during the day?
Yes. Spreads are tightest when the market is most active — during the overlap of the London and New York sessions — and widen outside those hours and around major data releases or central-bank decisions, when fewer participants are trading. For a one-off transfer on a major pair, the effect is small relative to the underlying trend.
Do I pay the spread twice if I convert back?
If you convert pounds into euros and later convert those euros back into pounds, you cross the spread on each leg and pay any margin twice. A round trip is therefore more costly than a single conversion, which is worth remembering if you are holding a currency temporarily rather than spending it — for example when funding a transfer to the United States that may not complete for some weeks.
Is the spread bigger for a forward contract?
A forward rate differs from the spot rate mainly because of the interest-rate gap between the two currencies, expressed as forward points — this is not the same as the bid-offer spread. Forward pricing is explained in our guide on why the forward exchange rate differs from the spot rate.
How do I see the real cost of a quote?
Note the mid-market rate at the moment you are quoted, then compare it with the dealt rate you are offered. The difference, converted into your transfer amount, is the total cost — spread and margin combined. Checking a live GBP/EUR reference and keeping an eye on the currency forecasts helps you judge both the cost and the timing.
Speak to a specialist about your transfer
If you are planning a large conversion and want to see the margin clearly rather than guess at it, request a quote from a Cambridge Currencies specialist. You will see the live mid-market reference rate, then receive a call from a dedicated dealer with your live trading rate and the margin disclosed up front — so you know exactly what the spread and the mark-up are costing before you commit.
