AllerCalc is a free and amazing tool to perform any mathematical operation you request. With this tool your work will be easier, it's perfect for accountants or engineers who are looking for fast and precise results. It comes with many useful features like making coin and measure conversions. In addition to that it has a virtual keyboard which you can use to enter numbers and symbolic characters. It has also a financial box with which you can calculate payments based on time.
It doesn't consume a lot of system resources and it's really easy to install and understand. Try it now!