# Dozecal — Duodecimal calculator

> Duodecimal RPN calculator for math and science education. (iPhone/iPad app by Johan Kovacs.)

- Source: https://appshunter.io/ios/app/dozecal/id1521160089 (this page in markdown: same URL + `.md`)
- Developer: [Johan Kovacs](https://appshunter.io/developer/1486605020)
- Category: Utilities, Productivity
- Price: Free
- Rating: 4.00/5 from 4 App Store ratings · 4 written reviews indexed
- Age rating: 4+
- Requires: iOS 12.0 · 27 MB
- Languages: English
- Released: 2020-07-02
- Data updated: 2026-06-04
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/dozecal/id1521160089/reviews.md

## What is Dozecal?

Dozecal is an educational RPN* calculator to promote the use of Base Twelve in math and science.
The usual math functions are available in both DUODECIMAL and DECIMAL modes.
Conversion is automatically made when switching from one mode to the other one.
Trigonometric operations uses DEGREE as unit of measure.

For more information about Base 12, please visit the Dozenal Society of America.


* RPN : the Dozecalc calculator uses the Reverse Polish Notation (RPN). This notation seems complex but has many advantages over algebraic notation and is more intuitive once you have understood the idea.

The calculator has a stack and any operation that requires two numbers is using the bottom stack layers (X and Y). Key ENTER to push the stack up and separate one number from the next. To perform arithmetic, key in the first number, press ENTER to separate the first number from the second, then key in the second number and then select and operator such as the numerical functions +, -, * or /. The result appears immediately after you press the numerical function key. The operator is keyed in only after both operands are in the stack.

Example: calculate 3 + 4
Key sequence: 3 ENTER 4 +
Result: 7 

The result of any operation may itself become an operand. You do not need to press enter again to use the result. The "7" is already entered. 

Example: add 2 to the previous result
Key sequence: 2 +
Result: 9

Example: calculate 5 * (3 + 4)
Key sequence: 3 ENTER 4 + 5 *
Alternate key sequence: 5 ENTER 3 ENTER 4 + *

Disclaimer: results and precision may occasionally be incorrect. Should you report them at johan@unumdesignum.com, and the author will be happy to fix !

## Key features

- Duodecimal and Decimal modes
- Automatic mode conversion
- RPN (Reverse Polish Notation) input
- Standard math functions
- Trigonometric operations (degrees)
- Educational tool for Base Twelve

## Recent user reviews (4 of 4)

All indexed reviews: https://appshunter.io/ios/app/dozecal/id1521160089/reviews.md

### 5/5 — Makes duodecimal Easy to understand

*2025-04-22, version 1.0.7*

I have been very interested in the base 12 system for a number of years now and I am very pleased there is a calculator app for it now. Very well thought out you can switch between the decimal and duodecimal modes.

### 5/5 — Really cool!!!!

*2023-03-26, version 1.0.3*

I’m learning dozenal at the moment and your calculator is pretty intuitive to understand, it’s neat learning RPN at the same time

### 5/5 — Another Excellent Improvement

*2023-01-31*

Great improvement in readability of fractional Dozenal numbers between 0 and 1!  Going immediately to scientific notation for numbers between 0 to 1 made them difficult to read.  This most recent update fixed that! 

Next suggestion:  Implement DSA font options for Dec and El (Pittman, Dwiggins, or both) in the display area?

### 1/5 — Interesting

*2020-07-28*

Has novelty value!
I get the feeling this is a 'work in progress', so I look forward to seeing how it develops.

Unfortunately, although the display rotates it does not resize for landscape view, meaning part of the keypad is missing and the readout is not visible at all!

…Reverting to portrait mode:
Stack behaviour is a bit odd: results are not automatically put into the X register, thus requiring an extra tap on the 'Enter' key to get them there.

Also, the keys themselves do not always register a hit, so watching the readout becomes a priority — and it's easy to make irretrievable errors.

It seems its most practical purpose is as a base10 / base12 conversion tool. However, I do like the concept and it comes without adverts, for free. Highly commendable!

## Frequently asked questions about Dozecal

### What is Dozecal?

Dozecal is an educational RPN calculator designed to promote the use of the duodecimal (Base Twelve) number system in math and science. It supports calculations in both duodecimal and decimal modes with automatic conversion.

### How does RPN work in Dozecal?

Dozecal uses Reverse Polish Notation (RPN), where numbers are entered first, followed by the operation. For example, to calculate 3 + 4, you would key in '3 ENTER 4 +'.

### Can Dozecal convert between decimal and duodecimal?

Yes, Dozecal automatically converts numbers when you switch between duodecimal and decimal modes, making it easy to work with both systems.

### What devices does Dozecal support?

Dozecal is available for iPhone, iPad, and iPod devices, indicated by its support for these platforms.

### What is the age rating for Dozecal?

Dozecal has an age rating of 4+, making it suitable for a wide range of users, including younger learners.

### How often is Dozecal updated?

The latest version of Dozecal is 1.0.9, and it was last updated on August 10, 2025, suggesting active development and maintenance.

### Does Dozecal have ads?

No, Dozecal does not contain advertisements, providing an uninterrupted user experience.

### Where can I learn more about Base Twelve?

For more information about Base Twelve, the app suggests visiting the Dozenal Society of America website.

## Version history (last 5 releases)

### 1.0.9 — 2025-08-10

Some minor bug fixes

### 1.0.7 — 2024-01-31

• Fixed: a wrong calculation with logarithms.
• Improved: one can now enter up to 20d (decimal) or 18z (dozenal) digits for a better precision.

### 1.0.6 — 2023-09-07

Bug fixes : ipad support in landscape mode and issue with y^x function.

### 1.0.5 — 2023-09-04

Switch to the PITMAN representation of 10d and 11d.
About section: f+EEX.
Bug fixes.

### 1.0.3 — 2022-11-20

• Avoid engineering notation for simple numbers such as 0;00000xyz, for better readability.
• A short RPN tutorial is available (EEX key).

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## More apps by Johan Kovacs

- [BETRIM News](https://appshunter.io/ios/app/betrim-news/id1486605021)

All apps by Johan Kovacs: https://appshunter.io/developer/1486605020

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-04.*