How to Size Bets with the Kelly Criterion (Free + Pro / Elite auto-sized)

Most bettors either flat-bet every pick the same or freelance their stake by vibe. Both leak money. The Kelly Criterion sizes each bet as a function of your edge and the odds, so bankroll growth is maximized without blowing up. NuroPicks auto-sizes every Pro/Elite pick at Quarter Kelly by default. This guide explains what the number means and when to override it.

Not financial advice. 1-800-GAMBLER. 21+ only.

The core idea

If you have an edge, bet bigger. If your edge is thin, bet smaller. If you have no edge, do not bet. Flat-staking ignores that picks are not equal. The Kelly formula turns edge into stake size:

Kelly % = (b * p - q) / b

p = your estimated win probability (from the model or your own read)
q = 1 - p
b = decimal odds minus 1 (i.e. the payout multiple on a win)

Result is the fraction of bankroll to stake. Half Kelly stakes half of that, Quarter Kelly stakes a quarter, and so on.

The fractional-Kelly scale

Full Kelly is mathematically optimal but psychologically unsurvivable. A 40% bankroll drawdown is normal variance at Full Kelly, and 40% drawdowns tilt almost everyone. NuroPicks defaults to Quarter Kelly for this reason.

Scale	Stake	Variance	When to use
Full Kelly	100% of formula	Brutal. 40-60% drawdowns are routine.	Never, unless you have an edge proven over 1000+ bets and iron stomach
Half Kelly	50% of formula	High. 20-30% drawdowns.	Experienced bettors with >500 tracked bets and verified edge
Quarter Kelly	25% of formula	Moderate. 10-15% drawdowns.	NuroPicks default. Sustainable for most users
Eighth Kelly	12.5% of formula	Low. Slow growth.	New bettors, unit-based bankrolls under $300, high-variance props
Flat 1u	Fixed 1%	Flat.	New users who want simplicity. Phase 1 bankroll hygiene

Concrete example

Your model says LAL -4.5 hits 58% of the time. The book is offering -110 (1.91 decimal).

p = 0.58, q = 0.42, b = 0.91
Full Kelly = (0.91 * 0.58 - 0.42) / 0.91 = 10.5%
Quarter Kelly = 2.6%

On a $1,000 bankroll, Quarter Kelly sizes this pick at $26. Flat 1u would have been $10. Your edge is strong enough to bet bigger, and Quarter Kelly captures that without betting the 10.5% a Full Kelly calculation would demand.

What `/bankroll` and `/picks` do automatically

/bankroll set 1000 locks your working bankroll.
/bankroll unit shows your current 1u size (1% default). Pro/Elite users see Quarter-Kelly override per pick.
/picks and /potd emit a per-user Kelly stake line on every embed. Format: Suggested: $26 (2.6% QK).
/kelly <p> <odds> runs the formula manually for any custom line.
/liquidity applies Kelly stake against book limits and splits across books if the stake exceeds a single book's max.

When to override down

Quarter Kelly is a default, not a law. Stake smaller than Kelly suggests when:

Props and exotic markets. Thin liquidity + model uncertainty = use Eighth Kelly or flat 1u.
Correlated slip. Parlay correlation flags orange or red (see /docs/HOW_TO_PARLAY_CORRELATION). Size the whole slip smaller.
Tail-heavy payouts. +500 or longer. Variance punishes you even with positive EV. Eighth Kelly.
Alpha run where probability is a guess. Early-season, small sample. Stake at half the Kelly you would normally use.
Emotional day. Tilt guard. If you chased a loss today, do not bet Quarter Kelly on the next one.

When to override up

Almost never. The only credible override is when:

You have a large verified sample (>500 bets) on this exact market type with a win rate matching your model.
The book is offering a clearly stale number (steam alert fired before close).

Even then, Half Kelly is the ceiling. Going to Full Kelly on a "hot" pick is how bankrolls die.

Common misreads

Using the book's implied probability as p. That gives you 0% edge by definition and a 0% stake. Your p must be independent of the line.
Ignoring the house edge. A -110 coin flip has negative EV. The formula returns a negative stake. Do not flip the sign - that is a "pass this bet" signal.
Compounding fractional-Kelly during drawdown. If bankroll halves, so does the dollar Kelly stake. Do not hold stake constant. /bankroll recomputes on every tracked settlement.

Related commands and pages

/bankroll set | unit | monthly - configure working bankroll and view per-user unit
/kelly <p> <odds> - manual calculator
/picks + /potd - auto-emit Quarter-Kelly suggestion per pick
/liquidity - Kelly stake vs book-limit split-across-books
/docs/GLOSSARY - Kelly Criterion, variance, bankroll, unit
/docs/COURSE_CURRICULUM - Module 4 (Free) covers bankroll + Kelly fundamentals; Module 9 (Pro) covers advanced Kelly + fractional scaling

Responsible gambling: bet sizing only works if the bankroll is money you can afford to lose. Set a deposit limit at the book before you open NuroPicks. 1-800-GAMBLER.