The Kelly Criterion answers one question: how much should I bet? It's a formula that calculates the optimal bet size based on your edge and the odds you're getting.
Bet more when you have a big edge. Bet less when your edge is small. Bet nothing when you have no edge. Kelly does this math automatically.
Use half Kelly, not full Kelly. If the calculator says bet 10%, bet 5% instead. This protects you from overestimating your edge, which everyone does.
Don't use Kelly until you've proven you're profitable over at least 100 bets. Track everything on paper first. If you can't beat the closing line, Kelly won't save you.
Kelly Criterion helps you bet more when you should and less when you shouldn't. It prevents you from overbetting when you're confident and underbetting when you've got a real edge. But it only works if you're honest about your win probability estimates.
When we first started using Kelly, we made it way too complicated. Here's the simple approach that actually works: use our free calculator, enter your bankroll and odds, and divide the suggested bet by 4 (quarter Kelly). That's it. Don't overthink it.
The hard part isn't the math—it's being honest about your win probability. If you're not sure, assume 52-53% for spreads at -110. That's conservative, but it keeps you from overbetting while you learn.