Enter the price you can trade and your independent probability estimate to see the expected value of one dollar at risk. When the result is positive, MaximizeROI converts the edge into a fractional-Kelly position that accounts for your bankroll.
Supply the available price and your forecast to calculate implied probability, expected return, and fractional Kelly exposure. A shareable URL preserves the exact assumptions behind the result.
YES price, $0.01 – $0.99
Your fair-value % for YES
Used to size the Kelly stake
Positive expected value
Back YES at $0.63
Your edge
+9.0%
ROI
14.3%
expected return per $1 staked
Payback period
7.00 bets
repeated bets to earn back one stake
Expected value
+14.3%
per $1 staked
Kelly bet size
12.2%
of bankroll · 0.50× Kelly
Recommended stake
$121.62
on YES @ $0.63
EV per share
+9.0¢
$0.09 profit per share
Kelly maximises long-run growth but assumes your probability is accurate. Most professionals size down to a fraction of full Kelly to blunt estimation error and variance. This tool is for education, not financial advice.
How to read this calculator
This tool shows your edge and the Kelly-optimal stake. Full-Kelly is aggressive — many traders use half-Kelly instead, betting only 50% of the Kelly fraction to balance growth with lower variance.
Want ROI, payback period, and a head-to-head against the industry baseline?
Confirm that your forecast beats the actual fill price, investigate why the two probabilities disagree, and limit exposure so a failed thesis stays survivable.
Positive expected value begins only when your probability estimate beats the contract's break-even probability. Quantify that difference before risking capital.
Compare forecasts with live pricesA wide gap between independent forecasts and traded odds marks a research candidate, not an automatic bet. Challenge the assumptions behind both numbers first.
Investigate probability gapsFractional Kelly turns an estimated edge into a smaller bankroll allocation. The reduction preserves room for forecast error and unexpected correlation.
Calculate a risk-adjusted stakeStart with the traded price and independent forecast, then inspect the evidence, central risk, and condition that would invalidate the apparent edge.
MaximizeROI connects prediction-market prices with economic data to surface divergences, explain forecasts, and report only the signals that matter.
Each email opens with the price-versus-forecast gap, then explains the evidence, the most important risk, and the event that could erase the opportunity.
One focused analysis daily, with no long-term commitment.
