RealCalc Scientific Calculator is Android's most popular scientific calculator. It has over 20 million downloads and more than 100,000 5* reviews.
RealCalc is designed to look and operate exactly like a real hand-held calculator. It has all the standard scientific functions plus history, memories, unit conversions and constants. You can choose from a number of display styles and formats. It also supports binary, octal and hexadecimal calculations and has an optional RPN mode. RealCalc is easy to use, but has full help included in the app.
If you like RealCalc, the pro version RealCalc Plus has lots of extra features including fractions, degrees/minutes/seconds, customizable conversions and constants, landscape mode, a home-screen widget, a 12-digit display and greater internal precision. Purchasing RealCalc Plus will also help to support further development. Just search for RealCalc Plus or follow the upgrade link in the app.