Kelly Criterion Calculator for Sports Bets
The Kelly criterion answers one question: given the price and your own estimate of the chance, what share of the bankroll should go on this bet? Enter the three numbers and the calculator gives the full Kelly stake and the safer fractions most bettors actually use.
Match report by: Nadia Ferreira-Holt·Checked by: Tobias Brandt·Updated
Most staking advice says “bet one to three per cent”. The Kelly criterion says how much, bet by bet, from the only two numbers that matter: the price on offer and your honest estimate of the chance. The answer is a share of the bankroll that grows it fastest over many bets, if the estimate is right.
Kelly stake calculator
Enter the price, your own estimate of the chance and your bankroll. The stake updates as you type.
- Price implies
- 0%
- Your edge
- 0%
- Full Kelly
- 0%
- Stake
- 0.00
3 sportsbooks, longest coin list first
Rakebit
Rocketpot
Wild.ioHow to use the Kelly calculator
- Enter the price in decimal, American or fractional form.
- Enter your chance in per cent. Not the bookmaker's: yours. The calculator shows what the price implies next to it, so you can see the gap.
- Enter the bankroll in the unit you bet in: USDT, bitcoin, or dollars.
- Choose the fraction. Half Kelly is selected by default, and for good reason, as the next sections show.
The formula, worked
Kelly's stake fraction is (b × p − q) ÷ b, where b is the decimal price minus one, p is your probability and q is one minus p.
Take a price of 2.10 and an estimate of 52 %. The price implies 47.6 %, so you see 4.4 points more than the bookmaker does. Then b = 1.10, and (1.10 × 0.52 − 0.48) ÷ 1.10 = 0.0836. Full Kelly says 8.36 % of the bankroll: 83.64 USDT on 1,000. Half Kelly says 41.82.
Why the estimate decides everything
Keep the price at 2.10 and move only your estimate:
| Your chance | Edge on the price | Full Kelly | Half Kelly on 1,000 |
|---|---|---|---|
| 54 % | 13.4 % | 12.18 % | 60.91 |
| 52 % | 9.2 % | 8.36 % | 41.82 |
| 50 % | 5.0 % | 4.55 % | 22.73 |
| 48 % | 0.8 % | 0.73 % | 3.64 |
| 47 % | −1.3 % | none | none |
Two points of estimate halve the stake. That sensitivity is the whole case for fractional Kelly. Nobody knows a match probability to the nearest point, and the cost of being too optimistic is worse than the cost of being too cautious: staking twice the true Kelly amount leaves roughly no long-run growth at all, while staking half of it keeps about three-quarters of the growth.
Where the probability comes from
The calculator cannot supply the estimate, and Kelly is only as good as it is. Three honest sources:
- Your own model or record. If you have a long record in one market, your hit rate at given prices is evidence.
- A sharper price elsewhere. If another board offers a tighter market, its prices, with the margin removed, are a reasonable estimate of the chance.
- The bookmaker's own price, de-margined. This gives a fair probability, but by definition no edge; Kelly will then say pass, which is the correct answer.
If none of these applies, Kelly gives a number with false precision. A flat stake of a small, fixed unit is the more honest choice, and our bankroll guide covers it.
Kelly with a crypto bankroll
Kelly works on the bankroll as it stands at the moment of the bet. In a stablecoin that is simple. In bitcoin or ether the bankroll moves with the coin between bets, so a stake sized on Monday's balance can be too big by Wednesday without a single bet being placed. Re-read the balance before each stake, and size in the coin you bet in, not in its dollar value.
Accumulators are a poor fit for Kelly: the combined probability is the product of several estimates, so the error compounds as fast as the price does. Use it on singles.
Related tools
The system bet calculator and the parlay calculator settle multi-leg slips. The deposit cost calculator shows what the bankroll loses on the way in.
Kelly assumes you can measure your edge, which starts with the price. The best odds board shows how to strip the margin from a line, and VIP crypto sports betting sites covers the ceilings that cap a full Kelly stake.