Guide
Currency conversion cost: mid-market rate, spread, fees and DCC explained
Every time you change money, two things can cost you: the exchange rate you’re given and the fees you pay. Fees are easy to spot, but the rate often costs more. This guide explains how to measure both against the mid-market rate, why a “no fee” offer can still be the most expensive, and what’s happening when a card terminal abroad offers to charge you in your home currency. It’s general education, not a recommendation of any provider.
To compare your own quotes, use the currency conversion cost calculator. It doesn’t fetch live rates: you enter the mid-market rate and each provider’s rate or markup yourself.
What is the mid-market rate?
In the wholesale currency market, there is a price at which dealers buy a currency and a slightly higher price at which they sell it. The mid-market rate is the midpoint between the two. It’s the rate you typically see quoted in financial news and market data, and it doesn’t include any provider’s margin.
Retail customers usually can’t trade at the mid-market rate, but it’s the fairest yardstick: the further a provider’s rate is from it, the more you’re paying.
A note on the Hong Kong dollar. The Hong Kong Monetary Authority (HKMA) runs the Linked Exchange Rate System, which keeps the Hong Kong dollar “within a band of HK$7.75-7.85 to one US dollar” (HKMA, checked 2026-10-04). That band applies to the market rate. A bank’s retail quote can sit outside it, at 7.95 for example, without any change to the peg: the difference is the bank’s spread.
What’s the difference between a spread and a fee?
- Spread (or markup): the gap between the mid-market rate and the rate you’re offered. It’s built into the rate, so it never appears as a separate charge.
- Fee: an explicit charge, either a fixed amount (such as HK$50 per transaction), a percentage of the amount, or both.
Cost of conversion = (what your money is worth at the mid-market rate) − (what you actually receive). It equals the spread cost plus all fees.
When the rate is quoted as home currency per unit of foreign currency (HK$ per US$, for example), the markup is:
Markup % = (offered rate ÷ mid-market rate − 1) × 100
At a mid-market rate of 7.80 and an offered rate of 7.95, the markup is (7.95 ÷ 7.80 − 1) × 100 = 1.923%.
How much does it cost to convert HK$10,000 to US dollars?
Say a provider offers 7.95 HK$ per US$ when the mid-market rate is 7.80, and charges a HK$50 fixed fee, taken from your HK$10,000 before conversion.
| Step | Calculation | Result |
|---|---|---|
| Amount after fee | HK$10,000 − HK$50 | HK$9,950.00 |
| Amount received | HK$9,950 ÷ 7.95 | US$1,251.57 |
| Value at mid-market | HK$10,000 ÷ 7.80 | US$1,282.05 |
| Shortfall in US$ | US$1,282.05 − US$1,251.57 | US$30.48 |
| Spread cost | HK$9,950 × (1 − 7.80 ÷ 7.95) | HK$187.74 |
| Fee | HK$50.00 | |
| Total cost vs mid-market | HK$187.74 + HK$50.00 | HK$237.74 (2.38% of HK$10,000) |
| Effective rate | HK$10,000 ÷ US$1,251.57 | 7.9899 HK$ per US$ |
The effective rate is the single number that captures everything: it’s what you actually paid for each US dollar, after the spread and the fee. In this example, the spread costs almost four times as much as the visible fee.
Fee before or after conversion?
Providers apply fees differently, so check the terms before comparing.
- Fee deducted first (as above): you hand over HK$10,000, HK$50 is taken, and HK$9,950 is converted. You receive US$1,251.57.
- Fee charged on top: the full HK$10,000 is converted and the HK$50 is charged separately, so you pay HK$10,050 in total. You receive US$1,257.86, and the total cost against the mid-market value of HK$10,050 is HK$238.68.
The effective rate is almost identical either way (7.9899 vs 7.9897). Make sure you compare like with like.
A fixed fee also hurts small amounts most. Converting HK$1,000 on the same terms leaves you with US$119.50, a cost of HK$67.92, or 6.79% of the amount.
Why can “no fee” still be expensive?
A provider that charges no fee can still widen its spread. Compare three hypothetical quotes for HK$10,000, all against a mid-market rate of 7.80:
| Quote | Rate (HK$ per US$) | Fees | You receive | Cost vs mid-market | Effective rate |
|---|---|---|---|---|---|
| A: rate + fixed fee | 7.95 | HK$50 | US$1,251.57 | HK$237.74 | 7.9899 |
| B: “no fee” | 8.00 | none | US$1,250.00 | HK$250.00 | 8.0000 |
| C: small markup + fees | 7.83 | 0.3% + HK$10 (HK$40) | US$1,272.03 | HK$78.16 | 7.8614 |
Fees are deducted before conversion in all three. Quote B advertises no fee, yet it delivers the fewest dollars. Quote C has the most fees, yet it delivers the most dollars. Ranking by the amount received or the effective rate, not by the headline fee, is the only comparison that works. The figures are illustrative, not real providers.
What is dynamic currency conversion (DCC)?
When you pay by card abroad, or withdraw cash from an ATM abroad, the terminal may offer to charge you in your home currency instead of the local currency. That’s dynamic currency conversion (DCC). If you accept, the merchant’s or ATM operator’s provider does the conversion at a rate it sets. If you decline, you’re charged in the local currency and your card issuer converts it, using the card scheme’s rate plus any foreign-currency fee in your card terms.
Card scheme rules require the choice to be yours:
- Visa says merchants and ATMs must display the amount in both currencies, the exchange rate and any additional fees or markup, and “must not choose on your behalf” (Visa, checked 2026-10-04).
- Mastercard’s DCC guide requires that no conversion method is the default, that the cardholder isn’t “steered” to DCC, and that the offer is “clear and neutral” (Mastercard DCC Guide 2025, checked 2026-10-04).
- In the EU, Regulation (EU) 2019/518 requires currency conversion charges on card payments to be expressed as a percentage markup over the European Central Bank’s reference rates, so payers can compare them (checked 2026-10-04).
To judge a DCC offer, divide the home-currency amount shown by the local-currency amount and compare that rate with the mid-market rate, just as you would for any quote. This is not a recommendation to accept or decline.
How do provider types compare?
No brands and no ranking: costs vary by provider, amount, currency pair and day. The table describes how each type typically charges, so you know what to enter in the calculator.
| Provider type | How the cost usually appears | What to enter in the calculator |
|---|---|---|
| Bank branch or app | Bank’s own buy/sell rate; sometimes a fixed fee for transfers | Offered rate, plus any fixed fee |
| Money changer (cash) | Spread built into the cash rate; usually no separate fee | Offered rate; fees at zero |
| Online money transfer service | Small markup or the mid-market rate, plus a fixed and/or percentage fee | Markup % or offered rate, plus both fees |
| Card payment in local currency | Card scheme rate plus the issuer’s foreign-currency fee, if any | Scheme rate as the offered rate, the issuer fee as a percentage |
| DCC at a terminal or ATM | Rate set by the merchant’s provider; markup built in | The rate shown on the terminal, fees at zero unless listed |
| Brokerage currency exchange | Broker’s conversion rate; sometimes a commission | Offered rate or markup %, plus any fee |
Whichever type you use, the method is the same: get the rate and every fee, enter them alongside the same mid-market rate, and compare the amount received.
Related guides
- US dividend withholding tax for non-US investors: relevant if you convert money to buy US shares.
- How compound interest works: small, repeated costs add up over time in the same way returns do.
Sources
- Hong Kong Monetary Authority, Linked Exchange Rate System (checked 2026-10-04)
- Visa, Decoding Dynamic Currency Conversion (checked 2026-10-04)
- Mastercard, Dynamic Currency Conversion Guide 2025 (merchant version) (checked 2026-10-04)
- EUR-Lex, Regulation (EU) 2019/518 on cross-border payments and currency conversion charges (checked 2026-10-04)
This guide is for general education only and isn’t financial advice. See our disclaimer.