Type the amount of money you want to convert and the codes of the two currencies, for example USD and EUR. The codes are only labels, so you can use any short name you like. Then enter the exchange rate. The rate means how many units of the second currency you get for one unit of the first.
This calculator does not pull live rates. That is a strength when you want a result you can trust, because you can type the exact rate shown by your bank, card company or money transfer service. The rate on your receipt is usually different from the middle market rate you see in the news.
If your provider charges a fee as a percentage, enter it in the fee box. The calculator takes the fee off the converted amount and shows what you actually receive. You will also see the reverse rate, which is handy for converting back, and the rate after the fee. That last number is the real price of the exchange, and comparing it between providers is the easiest way to find the cheapest option.
The amount before fee is: amount x exchange rate. The fee is that amount multiplied by the fee percentage divided by 100. What you receive is the amount before fee minus the fee.
The reverse rate is 1 divided by the exchange rate, and it tells you how much of the first currency one unit of the second currency costs. The rate after fee is the exchange rate multiplied by (1 minus the fee percentage divided by 100), and it shows the true rate you are getting.