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Value Betting

Value betting is the disciplined practice of placing trades only when your independent probability estimate indicates the contract is underpriced relative to its true likelihood, ensuring every trade has positive [[expected-value]] before execution.

Updated June 24, 2026Strategy & Analysis
TL;DR
Value betting means only trading when the price is wrong in your favor. Ignore contracts where you have no edge, no matter how much you like the outcome.

Key Points

✓A value bet requires that your estimated true probability exceeds the [[implied-probability]] from the contract price by enough to cover [[trading-fees]] and [[bid-ask-spread]].
✓Value betting is a process, not a prediction: you can be wrong on any individual trade and still be a successful value bettor if your probability estimates are well-calibrated over time.
✓Avoiding non-value trades is as important as finding value trades; unnecessary exposure to zero-edge contracts erodes bankroll through fees alone.
✓Value opportunities in prediction markets often cluster around information gaps: obscure events, niche domains, and slow-to-update markets.
✓Combining value betting with [[kelly-criterion]] sizing produces the theoretically optimal bankroll growth rate under accurate probability estimates.

The Value Betting Framework

Value betting begins before looking at any market price. A trader first forms an independent probability estimate for an event using available data, domain expertise, and Base Rate analysis. Only after arriving at this estimate do they compare it to the market Implied Probability. If the true estimate exceeds the implied probability after accounting for Vig and fees, a value bet exists. The size of the gap determines both whether to trade and how much to stake via the Kelly Criterion. This sequence matters: looking at the market price first contaminates your independent estimate through anchoring. Platforms like Kalshi and Polymarket quote prices in cents, making the comparison arithmetic straightforward once a clean probability estimate exists.

Sustaining Value Betting Over Time

The long-run profitability of value betting depends entirely on the accuracy of your probability estimates. Calibration research is therefore central to any serious value betting practice: tracking Brier Score or similar metrics across a portfolio of trades reveals whether your estimates are genuinely better than market prices or whether you are finding apparent value in noise. As markets grow more efficient and more informed participants compete for the same opportunities, edges narrow. Successful value bettors adapt by specializing in market segments where they hold durable informational or analytical advantages, rather than spreading attention across all available contracts. Rigorous Bankroll Management ensures that a losing streak, which is statistically inevitable even with positive Edge, does not end the trading operation.

Related Terms

Expected Value
Expected value (EV) is the probability-weighted average outcome of a trade, calculated by multiplying each possible payout by its estimated probability and summing the results. A positive EV trade is one where the anticipated return exceeds the cost over the long run.
Edge
Edge is the measurable advantage a trader holds over the market price of a contract, arising when an independent probability estimate differs favorably from the [[implied-probability]] reflected in the current price.
Kelly Criterion
The Kelly Criterion is a mathematical formula that determines the optimal fraction of a trading bankroll to stake on a single bet, maximizing long-run wealth growth by sizing positions in proportion to estimated edge.
Bankroll Management
Bankroll management is the set of rules a prediction market trader uses to allocate capital across positions, limiting per-trade exposure and total risk so that a losing streak does not result in ruin before long-run edge can play out.
Implied Probability
Implied probability is the likelihood of an event occurring as expressed by the current market price of a prediction market contract. On binary markets, a contract priced at 65 cents implies a 65% chance the event resolves YES.
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