Calc One: A capable, free and smart iPad calculator app

I'm not sure why Apple never put its Calculator app into the standard iPad software build, but the absence has opened the door for several enterprising developers to close the feature gap.

One nice new offering is Calc One, which was built specifically for iOS 8 but runs on any iPad running iOS 6 or later. The keyboard is arranged like a telephone keypad for easy entry, and the app provides both a standard simple calculator and scientific functions as well. A smart bar across the top of the keyboard gives you quick access to several scientific functions, and a history feature is built in so you can backtrack and see what calculations and numbers you entered. Colors can be customized, which is a nice touch many calculator apps don't offer.

Using Calc One was simple enough. I liked not having to tap the enter key to get results, although I had to get used to that. Some users might like a more standard keyboard for number entry, which should be an option. I preferred the telephone keypad-type layout, but some people may not and they should have a choice. As with Apple's calculator on the iPhone, advanced functions only appear in landscape orientation. I think users should get a choice of what they want to see in either orientation.

One thing I really didn't like was having a dialog box appear just after downloading Calc One asking if I was enjoying using the app. Well, I was until that happened. Developers need to give this kind of stuff a rest. Wait until I have really used the app a bit before asking me to rate it. You never get a second chance to make a first impression.

Other than those few negative points, I like Calc One a lot. There are other alternatives of course, like PCalc (US$9.99) which is probably the Holy Grail of calculators for scientists, students and engineers. It has a variety of skins, and is very customizable. PCalc also has a free version, and you can add specific functions as in-app purchases. But Calc One is also quite nice for a free app, has many functions, and works as advertised. I didn't hesitate to make it the only calculator on my iPad.

As mentioned, Calc One runs on any iPad running iOS 6 or later.