Platform independent versatile calculator for large numbers written in Java

Current version: 0.89c (23.11.2015)

Bitbucket Project Homepage
Details of the latest changes can be found here.

Calcutta is a console based calculator with scripting capabilities. The main purpose is to serve as a programmer's calculator, e.g. to convert numbers between different number systems. Since it represents all numbers by rational fractions internally, there are no errors introduced by rounding. E.g.
3*(1/3) is not nearly 1, but exactly 1. Furthermore, Calcutta's internal number representation is only limited by the RAM available. There is no restriction due to the typical 32bit or 64bit bounds of integers or doubles.

Calcutta Screenshot



Click link below to download and start Calcutta as a Java Webstart application.
If you don't have a Java runtime installed, you can find it here. Get and install JRE (Java Runtime Environment) to run Java applications (as Calcutta) or JDK to develop Java applications.

Calcutta  (click to install and start Calcutta via Webstart)
If you wish to have a "real" local installation, just download the JAR archive here. You can start it locally either by double clicking on it or manually using "java -jar calcutta.jar"

Note: Java Webstart will ask you for confirmation to give the application full access. Please do so, else Calcutta won't work. This is because Calcutta needs access to the file system to write its preferences and to load scripts. It does not contain any dangerous, hostile or otherwise malign code.
Calcutta will need at least Sun Java Runtime 1.4 installed. If not installed yet, you will be prompted if you want to install it. Once installed, you can also run Calcutta locally using the Java Webstart  Browser or by doubleclicking the desktop icon (if you chose to create one).

To learn more about Java, click here.
To learn more about Java Webstart, see here.


Name Volker Oth
Born 1971
Country Germany
Occupation Embedded C software development (automobile)
Contact You might contact me by mail if you have questions/bug reports/suggestions regarding Calcutta: VolkerOth (at)

Source Code

As of version 0.86, Calcutta became an Open Source project. All source files are released under the Apache License 2.0. In a nutshell that means you can use them and modify them even for closed source or commercial projects, as long as you leave some copyright info in and give appropriate credit. See the linked Apache License for details.
Each file of the source code should contain a header with the license information.

The whole source code, the icons and the HTML help are now stored in a Git repository hosted by Bitbucket.
I recommend to use SourceTree to handle the repository but there are several other tools and also Eclipse plugins.

Repository URL:


Calcutta is provided "as is" without warranty of any kind. Use it at your own risk.

Calcutta is freeware in the sense of "free for all to use". Download it, give it to your friends or whatever.
If you intend to put it as download on your site, please make a reference to official homepage. Same is true for distribution on magazine CDs/DVDs.
If you plan to distribute Calcutta as part of a commercial tool (which includes Shareware tools), please contact me before via Email.

As of version 0.86, Calcutta is also "free software", as all parts of the source are released under licenses approved by the Free Software Foundation. See chapter Source Code for details.

The algorithm to convert a periodic number into a rational fraction is inspired by the great German math site of  Arndt Brünner. Also some of the irrational Taylor approximation algorithms are based on his work.
Calcutta also uses a fast factorial algorithm by Peter Luschny.


There's a built-in HTML help describing all features. You can also read in online.