The conventional wisdom is 1-5% of your bankroll per unit, with conservative bettors sticking to the 1-2% range. Professionals typically use 1% because it allows them to weather losing streaks without significant bankroll damage. The issue with varying your unit size based on “confidence” is that most recreational bettors overestimate their edge on specific plays. If you’re going to adjust stakes, you need a documented track record showing which bet types actually perform better for you otherwise you’re just gambling on your gut feeling, which introduces emotional decision-making into what should be a mathematical process.