CurrencyApp is one of the simplest currency converters built to-date for macOS, converting currencies in seconds. All you need to do is select the currency that you are converting to; and enter the amount using the keyboard. That's it. This is a drop-dead easy application for this basic function of currency conversion.
Note: CurrencyApp is built to be working in online only. This app won’t be functional if your system does not have a working Internet connection.