Kelly Criterion Calculator — Prediction Markets
The Kelly Criterion is a mathematical formula for calculating the optimal fraction of a bankroll to bet on a favorable wager. For prediction markets, the formula is: f* = (bp - q) / b, where b is the net odds received (payout minus 1), p is your estimated probability of winning, and q is 1 - p.
If you believe a prediction market is at 60% but is priced at 50¢ (implying 50%), the market has a 10-point edge. The Kelly formula recommends betting approximately 20% of your bankroll on this position. Most professional traders use fractional Kelly (25–50% of the Kelly recommendation) to reduce variance.
FlowFrame's Kelly calculator integrates with live Polymarket and Kalshi prices — enter your probability estimate and it automatically calculates the Kelly-optimal position size and compares it to the current market price.