The Story Behind CalcIUM

Introduction

My name is Liubomyr.

Early development (2018)

In 2018, I started learning Java. To make the learning process more effective and engaging, I decided to build a real application instead of writing simple exercises — that’s how my first calculator was created.

It was a fairly simple project: a basic Reverse Polish Notation (RPN) algorithm, a minimal interface, Numeric and Function panels, as well as Settings and History screens. At that time, I had no intention of publishing the app — it was purely a learning tool. After finishing it, I moved on to other things and eventually forgot about it.

Return (2025)

In 2025, I had more free time and returned to programming as one of my favorite activities. I started working on several new applications and remembered my first calculator. Before moving forward with new projects, I decided to restore it and release it for free, without ads — simply so the work wouldn’t go to waste. I thought it might be useful to someone.

The app was restored and ready for release, but during the process I began adding new features. Step by step, this evolved into something much bigger, and I ended up focusing entirely on building a full-featured scientific calculator — CalcIUM.

Design goals

From the beginning, I had a clear goal: not to create just another generic calculator, but to build a tool that is precise, well-structured, easy to use, and visually refined. The most difficult part was maintaining the balance between simplicity and a wide range of functionality.

Accuracy

Accuracy became the first priority. CalcIUM was fully migrated from Double to BigDecimal — this applies to all calculations across the entire application. To ensure correctness, I implemented a large set of instrumental tests with thousands of expressions. As a result, CalcIUM reaches the level of accuracy found in the best scientific calculators.

Features

Then the functionality started to take shape. The following features were added:

• a unit converter with multiple categories and a wide range of values
• extended panels: SYMBOLS, BASE, CFG, STAT, FMT
• number base operations and bitwise logic
• an expanded set of mathematical and physical constants, along with SI prefixes
• time calculations (TIME)

Graphing

Special attention was given to graphing. CalcIUM supports function, parametric, and polar graphs. The goal was not just to display graphs, but to provide a complete toolset:

• multiple series on a single graph
• view control
• presets
• graph history
• PNG export
• JSON export

At the same time, the history system and interaction between values across panels were significantly expanded.

Design

Once the functionality reached the desired level, I moved on to design.

The light theme, Beach Pebbles, was created to feel calm and comfortable — something that makes even working with a calculator pleasant.

The dark theme, Starry Night, was designed to be more technical and strict, but with its own character.

Release and philosophy

Over the course of about a year, CalcIUM evolved into a complete product and was released.

I also made a deliberate decision to avoid ads entirely. The app contains no banners, no pop-ups, and no hidden mechanisms that push the user toward a purchase. The paid version unlocks extended functionality, while the free version already includes everything most users need, including function graphing and part of the unit conversions.

The purchase is one-time, with no subscriptions. The user decides whether additional functionality is needed.

CalcIUM was built with attention to detail and genuine interest in the process.

I hope it proves useful and enjoyable to use.