Multiply (Base to Foreign)
Divide (Foreign to Base)
Converted Total:
2. Find the Implied Exchange Rate
The Exchange Rate is:
(This means 1 unit of your base currency equals this many units of the foreign currency)
How to Work Out Exchange Rate on a Calculator
Understanding how to calculate currency exchange rates is a vital skill for travelers, international shoppers, and business owners. While online tools are convenient, knowing the manual math ensures you aren't being overcharged by hidden fees at a kiosk or bank.
The Core Formula for Currency Conversion
To convert from your "Home" or "Base" currency to a "Foreign" currency, you use the following formula:
Base Amount × Exchange Rate = Foreign Amount
Conversely, if you have a foreign amount and want to see what it's worth in your home currency, you reverse the math:
Foreign Amount ÷ Exchange Rate = Base Amount
How to Calculate the Exchange Rate You Were Given
If you have already performed a trade and want to know what rate the bank actually gave you (to check for hidden fees), use this formula:
Foreign Amount Received ÷ Base Amount Paid = Exchange Rate
Practical Example: Traveling to Europe
Imagine you have 500 units of your local currency and the exchange rate for Euros is 0.85. To find out how many Euros you will receive, you would enter 500 × 0.85 into your calculator, which equals 425 Euros.
If you return from your trip with 50 Euros and want to know its value in your home currency, you would calculate 50 ÷ 0.85, which equals approximately 58.82 units of your local currency.
Common Mistakes to Avoid
The "Spread": Banks buy and sell currency at different rates. Always ensure you are using the correct rate for the direction of your trade.
Hidden Fees: Sometimes a calculator says you should get 100 units, but you only get 95. The difference (5 units) represents the service fee or commission.
Inverse Rates: Be careful not to confuse a "USD to EUR" rate with a "EUR to USD" rate. One is usually the reciprocal (1 divided by the other) of the first.
function calculateConversion() {
var amount = parseFloat(document.getElementById('amountToConvert').value);
var rate = parseFloat(document.getElementById('conversionRate').value);
var direction = document.getElementById('conversionDirection').value;
var resultDisplay = document.getElementById('conversionResult');
var resultValue = document.getElementById('convertedValue');
if (isNaN(amount) || isNaN(rate) || rate <= 0) {
alert("Please enter valid positive numbers for both the amount and the exchange rate.");
return;
}
var total;
if (direction === "multiply") {
total = amount * rate;
} else {
total = amount / rate;
}
resultValue.innerText = total.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 4});
resultDisplay.style.display = "block";
}
function calculateImpliedRate() {
var paid = parseFloat(document.getElementById('basePaid').value);
var received = parseFloat(document.getElementById('foreignReceived').value);
var resultDisplay = document.getElementById('rateResult');
var resultValue = document.getElementById('impliedRateValue');
if (isNaN(paid) || isNaN(received) || paid <= 0) {
alert("Please enter valid numbers. The amount paid must be greater than zero.");
return;
}
var rate = received / paid;
resultValue.innerText = rate.toFixed(6);
resultDisplay.style.display = "block";
}