Lesson 11 of 12 · 5 min
Kelly for beginners
Kelly calculates a share of your bank based on your edge. The picture shows two labels: full 8% and ¼ 2%. The formula assumes you know your chance. A beginner does not know their chance; they feel it. Full Kelly on a mistaken "I make it 56%" stakes far too much. That is why the school shows you the formula and keeps you on flat 1%. This is a lesson in literacy, not a switch to Kelly from Monday.
Kelly for beginners in plain words
A beginner needs Kelly as a vaccine against two myths. Myth 1: "smart bettors always use Kelly". Myth 2: "Kelly guarantees a profit". The formula is: share ≈ (b·p − q) / b, where b = odds − 1, p is your chance and q = 1 − p (p being your estimate of the probability). If p is wrong, the share is wrong. Quarter Kelly softens an error in p. Flat 1% softens it even more and does not require you to estimate p as a percentage for every match. Over your first hundred bets, that matters more than being "optimal".
How it works
Work through the textbook example, write it down and close the calculator. Do not use Kelly at the bookmaker until your diary holds 100 singles with p estimated before the match. If you write down p after a goal, it is not p. If your edge is "about five percent or so" with no number, it is not an input for the formula. Bonulist does not calculate Kelly for you and does not accept bets.
- Estimate p out loud before looking at the odds, and write it down.
- Calculate full Kelly on paper.
- Take a quarter and compare it with 1 unit (one stake, usually 1% of the bank).
- Stake 1 unit anyway, for as long as you are on this course.
Example with numbers
Home win at odds of 1.91, so b = 0.91. You estimate p = 56% (0.56), so q = 0.44. The numerator is 0.91 × 0.56 − 0.44 ≈ 0.07. The share is ≈ 0.07 / 0.91 ≈ 8%: full Kelly, as in the picture. A quarter is ≈ 2%. The school's flat stake is 1%. If your 56% is really 50%, full Kelly is already toxic, a quarter is unpleasant, and 1% will survive the mistake. That is why the picture shows 8% as a warning, not a target.
| Method | Share in the example | What it requires |
|---|---|---|
| Full Kelly | ~8% | An accurate p |
| Quarter Kelly | ~2% | The same p, more gently |
| School flat stake | 1% | Discipline, not an accurate p |
Common mistakes
- Using full Kelly because "that is what the article said".
- Adjusting p until the formula allows 5 units.
- Mixing Kelly and chasing on the same evening.
- Reading a negative Kelly as "I should bet against it". That is a different sport.
What to write in your diary
A practice line: p, odds, full, ¼, actual stake 1 unit. Do not confuse the practice line with a real bet.
Kelly criterion, flat staking, value. Next: bankroll rules.
18+ only. This is a lesson, not a tip or a call to bet. Bonulist is an editorial guide to licensed bookmakers; we do not take bets.