For the following reasons, I think this calculator for the best available for Android:
+ No special permissions needed
+ Good appearance, reasonable placed buttons and thus
+ Easy to operate
= Many functions, including many unit conversions (eg ° F in ° C)
- In the standard colors of the 2nd key is not easy to recognize, with the second function of a key is reached
I have the app as a gift from Amazon get (Free App of the Day) and has since been used much. Precisely because of the app permissions (no) and because no unnecessary Internet connection is necessary, can I further APP piles only fully.