The Kelly System
The Kelly system is a betting system. It can be used for gambling or investing. If you are unfamiliar with the Kelly system you can look at this short introduction.
For a more detailed introduction to the Kelly system that includes mathematical derivations and algorithms for calculating the Kelly fraction, see our book Bet Smart: The Kelly System for Gambling and Investing.
Below is a list of calculators that can be used to calculate the Kelly fraction and run simulations using the Kelly system. Note that these calculators and simulators are for educational purposes only and should not be relied upon for making investment decisions.
- Coin Toss Calculator - this is for the simplest case where you have only two possible outcomes.
- Single Bet Calculator - this is for the more general case of a single bet with any number of possible outcomes.
- Two Bet Calculator - this is for the case of two independent bets, each with any number of possible outcomes.
The Kelly system can also be applied in ways that go beyond being a simple money management system. One interesting application is to use it to calculate bond default probabilities. See our: Bond Default Probability Calculator.
Below is some free open source software that can be used to calculate Kelly fractions and run simulations. If you are looking for some Kelly application software not covered you can contact Stefan Hollos (stefan at exstrom dot com).
- kelly.py contains functions for calculating Kelly fractions for a single bet and two independent bets. The functions are written in the Python programming language. The single bet fraction is calculated with kfsingle(rv, pv) and the two bet fraction is calculated with kfidouble(rv1, rv2, pv1, pv2). See the file for more documentation.
- kelly.ods is a spreadsheet for calculating the kelly fraction and doing simulations for a coin toss bet, a single bet or two independent bets. It is an OpenOffice spreadsheet. OpenOffice is a free alternative to Micosoft Office that runs on Windows, Linux, Solaris, and Mac operating systems. The spreadsheet contains macros which perform some of the calculations. You may have to change the security level to allow these macros to run. To change the security level, go to the tools menu and choose options. In the dialog box choose security under the OpenOffice.org heading and click on the Macro Security button. Choose the Medium security level.