NFL Weekly Slate Kelly Calculator

What is the Kelly Criterion?

The Kelly Criterion is a mathematically derived formula for determining the optimal fraction of your bankroll to wager on a given bet. Developed by Bell Labs scientist John L. Kelly Jr. in 1956, it solves a specific problem: given a known edge, how much should you bet to maximize long-run growth without risking ruin?

The core formula is straightforward. If p is your probability of winning, q = 1 – p is the probability of losing, and b is the net decimal odds (e.g. –110 American odds converts to b ≈ 0.909), then the Kelly fraction is: f* = (b × p – q) / b. The result tells you what percentage of your bankroll to risk on that game.

What makes Kelly powerful is that it's both aggressive and self-correcting. Bet more when your edge is large, less when it's thin, and nothing when there's no edge at all. Over a long series of bets, full Kelly sizing produces the maximum possible geometric growth rate — no fixed-unit or percentage system can match it in theory. In practice, most serious bettors use a fractional variant to smooth out the variance.

Full Kelly, Half Kelly, and Quarter Kelly

Full Kelly is mathematically optimal but brutal in practice. The swings can be severe enough to cause most bettors to abandon the system mid-drawdown — at exactly the wrong time. It also assumes your probability estimates are perfectly accurate, which they never are.

Half Kelly (multiply f* by 0.5) cuts the volatility significantly while preserving roughly 75% of the long-run growth rate. It's the most widely recommended approach among quantitative bettors and is the default in this calculator. Quarter Kelly further reduces variance and is appropriate when you have meaningful uncertainty about your edge estimates — which, if you're honest, is most of the time.

A useful rule of thumb: the more uncertain you are about your probability estimates, the more you should shade toward fractional Kelly. Overconfident Kelly sizing is one of the most common ways disciplined bettors blow up their bankrolls.

How to Use This Calculator

1. Set your weekly bankroll. This is the total amount you've allocated for the week — not your lifetime bankroll. The default is $1,600, which corresponds to 16 games at $100 per unit. Adjust it to match your actual weekly allocation.
2. Set your default odds. For standard NFL ATS bets, –110 is correct and applies to every row. If you're shopping lines and have a game at a different number (e.g. –105 or –115), edit that row's odds individually after loading.
3. Choose your Kelly fraction. Start with ½ Kelly unless you have a strong reason to do otherwise. Full Kelly is only appropriate if you have high confidence in your probability estimates.
4. Choose your allocation method. Normalized distributes your entire bankroll proportionally across all positive-edge games — the wager column will always sum to your full bankroll. Raw Kelly sizes each bet independently as a percentage of bankroll, so the total deployed can be more or less than your full amount. Normalized is the practical choice for weekly slate betting; Raw Kelly is better for evaluating individual bets in isolation.
5. Enter your cover probabilities. Each row takes a win probability between 1 and 99. These should come from your own model or handicapping process — the calculator doesn't generate them. Games with a probability at or below 50% have no positive edge at standard odds and will automatically show $0 and dim in the table.
6. Read the output. The Kelly f* column shows the adjusted fraction (after applying your chosen multiplier). The Wager column shows the dollar amount to bet on that game. The summary row at the bottom shows your total deployment, average edge across the slate, and your largest single bet.
7. Add or remove games. Use + Add game to extend the slate beyond 16 games or build a partial week. Use the ✕ button to remove any game you're skipping. The calculator recalculates instantly on every change.