A free app for Android, by ARPAPLUS.

The application is easy to use and lets you perform simple calculations such as adding or subtracting numbers, multiplying or dividing by a number, or converting from one unit to another. It also supports more complex calculations, such as finding the area of a circle, the distance between two points, or calculating the average of a set of numbers.

You can also add the current date and time to a calculation, which makes it easy to see the result in a different format, depending on what unit you want to convert.

The application has an option to use the units that you are most familiar with, such as feet and inches, kilometers and miles, pounds and ounces, etc. The application also supports the most common currencies, such as the U.S. dollar, the British pound, the euro, the Japanese yen, the Canadian dollar, etc.