function calculateConversion() {
var amount = parseFloat(document.getElementById('sourceAmount').value);
var rate = parseFloat(document.getElementById('exchangeRate').value);
var markup = parseFloat(document.getElementById('bankMarkup').value);
var fixedFee = parseFloat(document.getElementById('fixedFee').value);
// Validation
if (isNaN(amount) || amount <= 0) {
alert("Please enter a valid source amount.");
return;
}
if (isNaN(rate) || rate <= 0) {
alert("Please enter a valid exchange rate.");
return;
}
if (isNaN(markup)) markup = 0;
if (isNaN(fixedFee)) fixedFee = 0;
// Logic
// 1. Calculate what the raw conversion would be without fees (Mid-market "Google" value)
var rawValue = amount * rate;
// 2. Calculate the "Spread Loss"
// Banks usually take the spread by offering a lower rate.
// Effective Rate before fixed fees = Market Rate * (1 – Markup%)
var markdownDecimal = markup / 100;
var effectiveRatePure = rate * (1 – markdownDecimal);
var valueAfterSpread = amount * effectiveRatePure;
var spreadLossAmount = rawValue – valueAfterSpread;
// 3. Handle Fixed Fee
// Fixed fee is usually deducted from the source amount before conversion,
// OR deducted from the final amount.
// For this calculator, we will treat the fixed fee as a cost deducted from the SOURCE amount to handle standard wire logic.
// Formula: (Amount – FixedFee) * EffectiveRate
// However, to show "Loss" clearly, let's calculate the value of the fee in target currency.
// Scenario A: Fee is in Source Currency.
var amountAfterFixedFee = amount – fixedFee;
if (amountAfterFixedFee < 0) {
alert("Fixed fees differ greater than the amount sending.");
return;
}
var finalValue = amountAfterFixedFee * effectiveRatePure;
// Calculate the specific loss attributed to the fixed fee in target currency terms
// It is roughly (FixedFee * EffectiveRate)
var feeLossInTarget = valueAfterSpread – finalValue;
// Display Logic
document.getElementById('resultBox').style.display = 'block';
document.getElementById('rawConversion').innerHTML = rawValue.toFixed(2);
document.getElementById('spreadLoss').innerHTML = "-" + spreadLossAmount.toFixed(2);
document.getElementById('feeLoss').innerHTML = "-" + feeLossInTarget.toFixed(2);
// Effective Rate = Final Value / Original Source Amount
var trueEffectiveRate = finalValue / amount;
document.getElementById('effectiveRate').innerHTML = trueEffectiveRate.toFixed(4);
document.getElementById('finalAmount').innerHTML = finalValue.toFixed(2);
}
Why the "Google Rate" Isn't What You Get
When you search for "currency conversion rate" on Google, the number you see is known as the mid-market rate or interbank rate. This is the midpoint between the "buy" and "sell" prices of two currencies in global currency markets. While this is the truest indicator of a currency's value, it is essentially a wholesale rate available only to large banks and financial institutions trading billions of dollars.
Regular consumers and small businesses rarely get this rate. Instead, banks and exchange services apply a spread (markup) and additional service fees. Our calculator above helps you determine the real cost of your transfer by factoring in these hidden variables.
How to Calculate Your Real Exchange Rate
To understand how much money will actually arrive in the destination account, you need to look beyond the headline rate. The formula used by most retail banks involves two main costs:
The Exchange Rate Markup: Most banks add a margin of 2% to 5% onto the mid-market rate. If the Google rate for USD to EUR is 0.90, a bank might offer you 0.87. This difference is pure profit for the bank.
Fixed Transfer Fees: This is a flat fee charged per transaction (e.g., $15 or $30), regardless of the transfer amount.
Using the Calculator
This tool allows you to input the current rate you see on Google or financial news sites, and then adjust it based on the fees your bank quotes.
Amount to Send: Enter the total amount of source currency you wish to transfer.
Market Rate: Enter the current rate found on Google (e.g., if searching "1 USD to GBP", enter the result).
Bank Markup: Enter the percentage your provider charges. If you don't know, 2.5% is a standard conservative estimate for major banks.
Fixed Fee: Enter any flat wire transfer fees charged by your bank.
The "Recipient Actually Gets" field shows the net amount after all these hidden costs are removed, giving you a realistic expectation for your international transfer.
Example Calculation
Imagine you want to send 1,000 USD to Europe.
Current Google Rate: 0.92 EUR per USD.
Bank Markup: 3%.
Wire Fee: $20.
Without a calculator, you might expect the recipient to get €920. However, after the $20 fee is removed (leaving $980) and the 3% markup is applied to the rate (reducing it to ~0.892), the recipient might only receive roughly €874. That is a difference of €46 simply due to fees and spreads.