Kelly Criterion Experiments

How much of your bankroll should you bet when you have an edge? Bet too little and you leave growth on the table. Bet too much and a losing streak wipes you out. The Kelly criterion gives the mathematically optimal answer — the fraction that maximizes long-run wealth growth.

This project implements the Kelly formula, simulates wealth trajectories across different bet-sizing strategies, and visualizes why overbetting is just as dangerous as underbetting.
View source on GitHub →

f* = p − (1 − p) / b     where p = win probability, b = net odds

Overview

Three plots in one figure: (1) optimal fraction vs win probability for different odds, (2) optimal fraction vs odds for different probabilities, (3) wealth evolution comparing no bet, ¼ Kelly, ½ Kelly, full Kelly, and 1.5× Kelly over 500 bets.

Kelly Criterion overview plots

Monte Carlo Experiments

Each image below is an independent 50,000-bet simulation with a fresh random seed. Curves range from 0.1× to 4× Kelly plus all-in. Notice how 0.8× Kelly consistently dominates — and anything above 2× Kelly gets crushed by variance. Click any image to enlarge.

10 independent runs · p = 0.995, b = 0.01, f* = 0.495 · log scale