Here are Calcularium users describing the app:

You know how you're slowly calculating something and you're in the middle of an expression so you want to know how you're doing? Yeah well that's real time calculation and I couldn't find an app that did it right, tried dozens of them and still nothing, BUT this app does it the perfect way, actually the way it should work, this app is definitely worth it, thanks a lot devs, big love.

Edit: OMG this is better than I thought, I just noticed the tutorials given and this app has more functions than I noticed, this is super amazing, devs, you're the best.
– Anton31kah10

I mean it literally. The tiny app packs impressive amount of useful stuff for a mere calculator. I would say it’s like mobile Excel. Math functions, unit conversion, currency exchange rates, and, even simple programmers functions. I wrote a small formula to calculate tips for our county. Easier and better than any tipping app!

I hope the developer expands these functions for Shortcuts and Siri. This would be real killer app! Thanks guys!
– Z!KeepeR

What looks like just a clean calculator app is in fact a powerhouse full of advanced features you could only get with custom Excel mega sheet.
– AlexDbk

You can find a lot of different kind of calculators but this is something completely new and awesome. It is not an another boring calculator. This is your real helper if you need to calculate something more than 2+2 :). Tutorial is great and helpful. History, customizable functions, variables, converter and much more. Great! It is definitely the next generation of the regular things.
– Lysyk

CALCULARIUM FEATURES:

• Voice-controlled, backed by Siri

• Script and Photo input modes

• Reactive Calculations

• Multi-Level Sub-Calculations with No Limits

• History: Editable and Reusable

• Self-Explanatory Naming for Every Componen

• Functions and Reusable Expressions

• Constants and Reusable Numbers

• Multiple Reversible Conversions (350+ units and 160+ currencies)

• Advanced Search

• Built-In Scientific Functions

CONTROL BY VOICE

Calcularium is also can be controlled by voice and has the ability to understand spoken math questions and calculate the answer. Tell it: "6 bottles by 15 dollars” - and it will give you the right result! It works by using verbal numbers and mathematical operations.

FLUID DESIGN

The design language of the Calcularium is based on tokens. All tokens are of the same structure: the left part shows a type of the element, the right part has a result or an entered value and its name on top. In addition to tokens there are pure numbers and math operators.

HISTORY

You can set an expression as a variable with the goal to use it afterwards in other expressions and give every component a clear name to recall what it stands for easily. Create a calculation, and next time you reuse it from History section, every component will clearly speak to you.