How do you decide your bet size as a percent of your bankroll?

What percent of bankroll should one bet be?

For most bettors, a single bet should be small enough that a losing streak does not damage decision quality. Many disciplined bettors cap one play around 1% to 3% of bankroll, even when a formula flashes something larger.

That cap is not cowardice. It is variance management with a cleaner haircut.

Kelly fraction = edge / odds, expressed as a percent of bankroll; most disciplined bettors bet a fraction (quarter to half Kelly) to control variance. A practical workflow keeps the math in one order. Price the market first, convert everything to probability, compare against your projection, and only then think about stake size. Reversing that order is how bettors talk themselves into action before they know whether the number is actually playable.

How does Kelly convert edge into bet size?

Kelly sizing turns edge and odds into a bankroll percentage. In common betting language, the Kelly fraction is the edge divided by the net odds, with the edge estimated from your fair probability versus the market price.

The input matters more than the calculator. If your edge estimate is inflated because you used a juiced sportsbook price instead of a no-vig baseline, the stake will be too aggressive.

Kelly fraction = edge / odds, expressed as a percent of bankroll; most disciplined bettors bet a fraction (quarter to half Kelly) to control variance. A practical workflow keeps the math in one order. Price the market first, convert everything to probability, compare against your projection, and only then think about stake size. Reversing that order is how bettors talk themselves into action before they know whether the number is actually playable.

For product work, keep the loop explicit: use Kelly Criterion Calculator and No-Vig Calculator for the math, then use Bankroll Safety Rules to audit the assumptions behind the number.

Why do bettors use quarter Kelly or half Kelly?

Full Kelly maximizes theoretical bankroll growth when your probabilities are accurate. Real bettors have imperfect models, changing markets, and bad Tuesdays, so smaller fractions are usually smarter.

Quarter Kelly and half Kelly reduce drawdowns and make model error less expensive. Sharkie respects the math, then trims the fins.

For product work, keep the loop explicit: use Kelly Criterion Calculator and No-Vig Calculator for the math, then use Bankroll Safety Rules to audit the assumptions behind the number.

When should you override the Kelly output?

Override Kelly when the market is thin, the injury news is unstable, the line moved away from your entry, or the bet is correlated with other exposure you already hold.

A hard cap keeps one bad estimate from doing too much damage. Bankroll rules should be written before the bet, not negotiated after the espresso hits.

Write the inputs down before the bet: market price, fair probability, model probability, edge threshold, stake fraction, and the reason the number could be wrong. That small audit trail makes it much easier to separate a good losing bet from a bad winning one.