I would like to share my favorite calculator app that I’m using as an engineer. The basic calculator provided with your smartphone or tablet may be sufficient for most situations. However engineering I feel that I need more. After trying several calculator app in the past I ended with two only, and a bonus one!

## 15C Pro Scientific Calculator, for the HP Calculators Lovers

“15C Pro Scientific Calculator”, by Vicinno Soft LLC, www.vicinno.com, for iOS and Android.

15C Pro Scientific Calculator App is one emulation of the HP 15C, a pocket calculator from the 80’s. This is really for the HP calculators lovers! I have the HP15C since the middle school and I’m still using it as an engineer! It is so robust and I appreciate the feeling of the keys. To be clear, it’s a favorite app because I like the genuine HP15C.

But let’s talk about the app! That will be very short: it’s like the original HP15C, except for the touch sensation. It’s better to describe the actual tool.

The HP15C, like many of the HP calculators is using the Reverse Polish Notation (RPN). With this system there is no brackets and no equal sign. Those three symbols are replaced by the ENTER key. I’ll show you two examples.

To calculate 3 + 2:

Classic Calculator | RPN Calculator |

3 | 3 |

+ | ENTER |

2 | 2 |

= | + |

With this first example you’ll ask me that is the point of “complicating” the things!

Let see now how to calculate 5 × (3 + 2):

Classic Calculator | RPN Calculator |

5 | 3 |

* | ENTER |

( | 2 |

3 | + |

+ | 5 |

2 | * |

) | |

= |

With this basic calculation you gain 2 keystrokes! That’s the magic of this system.

More about RPN : https://www.hpmuseum.org/rpn.htm or here https://en.wikipedia.org/wiki/Reverse_Polish_notation.

The HP15C is a scientific calculator. It solves the roots of equations, does numerical integration, supports complex numbers and matrix operations. And it calculates the classic mathematical and probability functions. It is also programmable.

## Tydlig, simple look and powerful use

“Tydlig”, by Tydlig Software AB, www.tydligapp.com, only for iOS.

The second calculator app, Tydlig, is completely different. I summarized it with two words: simple and powerful.

The best introduction is to visualize the YouTube video from the editor.

As you can see, you just type your calculation and you can modify it. It means you’ve got a programmable calculator without having to program anything! For everyday life, at home or in the office, I use this app quite a lot, in particular for corner table calculations. No need to open Excel and type your formula. Tydlig allow to do it much faster.

I find the concept and the interface so neat that I always recommend it to my colleagues.

## One more? WolframAlpha

The web search engine WolframAlpha (see my post here) is also available as an app (https://products.wolframalpha.com/mobile/) for iPhone, iPad, Android, Kindle Fire and Windows Phone/Tablet.

It has not exactly the same use as the calculators discussed above. I would say it is complementary. Not to do simple calculations, but more to solve equation roots, integral, differential equations and much more.

The WolframAlpha app, like the web version, is a scientific reference / search engine. WolframAlpha said it is a knowledge tool that instantly computes « answers to questions across thousands of domains—from finance and food to math and medicine to stocks and spacecraft to wordplay and weather… ».

However, as I explained in my post, the use of the search needs some practice and experimentation to get what you want. That’s not a problem for me, since there is a learning curve for most tools you start using.

## What about you?

I’m very interested to know which calculator app for engineer you are using. Feel free to comment below.