What is the Currency Exchange Margin Calculator?
Banks, money-transfer apps and airport bureaus rarely charge an upfront fee. Instead, they bake a hidden margin into the exchange rate — giving you a rate that is worse than the real "mid-market" rate you'd see on Google or Reuters. This calculator measures that hidden markup as a percentage and shows the actual money it costs you.
How to use it
Enter three values: the amount you converted (in the source currency), the mid-market rate at the time, and the offered rate you actually received. The calculator returns the markup percentage and the cost of that markup. Anything above roughly 1% is expensive for major currency pairs.
The formula explained
The markup is the gap between the true rate and your rate, expressed relative to the true rate: $$\text{Markup \%} = \frac{\text{Mid-Rate} - \text{Offered Rate}}{\text{Mid-Rate}} \times 100$$ The cost is simply that percentage applied to the amount you converted: $$\text{Cost} = \text{Amount} \times \frac{\text{Markup \%}}{100}$$ Because the cost is expressed in the source currency, it represents how much value you effectively lost in the conversion.
Worked example
Suppose you converted 1,000 USD when the mid-market EUR/USD rate was 1.1000, but you were offered 1.0800. The markup is $$\frac{1.1000 - 1.0800}{1.1000} \times 100 = 1.818\%$$ On 1,000 USD that's a cost of about 18.18 — money the provider kept as a hidden spread.
FAQ
Where do I find the mid-market rate? Search the currency pair on Google, XE or Reuters at the time of your transaction — that is the unmarked benchmark rate.
What is a fair markup? For major pairs, specialist providers charge 0.3–1%. Banks and airport kiosks often charge 3–8%.
Does this include flat fees? No — this measures only the rate margin. Add any fixed transfer fee separately for the total cost.
