RpnCalc is the best RPN calculator on the Android Market. It has an interface that users RPN calculators will be completely at home with, including these features: Scientific mode Basic (large key) mode 20 Memories Key click (haptic feedback) Continouous memory 16-level stack (configurable) Front four stack elements displayed RpnCalc has a sixteen-level stack to hold more data. The front four elements on the stack are visible at all times, making it much easier to keep track of where you are in your calculations. "Calculator tape" records your calculations and can be shared via email, bluetooth, etc. See http://www.efalk.org/RpnCalc/ for manual Oh, and here's the privacy policy: RpnCalc never collects any private data of any sort. It never connects to the internet. It doesn't even run ads.