The Kelly calculator helps you turn an edge into a recommended bet size using the Kelly Criterion. To use it, enter your bankroll, choose a Kelly multiplier such as 1 for full Kelly or 0.25 for quarter Kelly, add the odds, and input your projected win probability to calculate a suggested wager amount. For example, if your bankroll is $1,000, the line is -110, your projected win probability is 55%, and you use 0.25 Kelly, the calculator will suggest a smaller and more conservative stake than full Kelly. It is a useful tool for sizing bets with discipline instead of relying on guesswork.