This is a calculator that uses the outstanding way of entering numbers HP uses in their calculators, called RPN, Reverse Polish Notation. I have been missing a calculator like this for Windows for many years. I am not able to use the calculator that is shipped with Windows as I am too used to RPN. HP did ship a RPN calculator a few years ago with their Vectra PC's but that one, and Microsoft's calculator, is somewhat space demanding on your desktop.

I have found several RPN calculators on the Internet but all of them are very ambitious, some even in Java to be used in a browser, not very user friendly. There is actually no need for a Windows calculator that looks like a real one and buttons to press with your mouse.

So, I have designed a really minimal calculator that takes very little space on your desktop and on your disk. It does not have any fancy features at all, just the basic ones. It is so small it can be open at all times, just use it when you need to.

Please, download it, test it and let me know what you think, I really appreciate if you would. The file is less than 30kB and does not require any installation. Give it to anyone you think could be interested but you may not charge anything for it and please give me credit.

RPNCalc.zip (<30kB) version 2.1.1

If you want to know more about RPN:


Tomas Rudh
Stockholm, Sweden