Free Kelly Criterion Calculator 2026
Calculate optimal bet sizes using the Kelly Criterion – the mathematically proven formula for maximizing long-term growth. Full Kelly, half‑Kelly, and quarter‑Kelly included. Used by 20,000+ advantage players.
📈 Interactive Kelly Calculator
e.g., 50% = 0.5
Optimal Bet Sizes
📘 How to Use the Kelly Calculator
Enter Bankroll
Input your current bankroll – the total money you've allocated for betting.
Enter Odds & Probability
Provide the odds (American or Decimal) and your estimated chance of winning (0–100%).
Get Your Kelly Bet
Click 'Calculate' to see full Kelly, half‑Kelly, and quarter‑Kelly bet sizes. Use half‑Kelly for reduced volatility.
🔍 Understanding the Results
Full Kelly
The mathematically optimal bet size to maximize long-term growth. Can be aggressive; may cause large swings.
Half‑Kelly / Quarter‑Kelly
Fractional Kelly reduces volatility while preserving most of the growth. Recommended for most bettors.
Edge
Your advantage over the bookmaker: (probability × decimal odds) – 1. Positive edge = profitable bet.
Negative Edge
If edge is negative, Kelly recommends no bet. The calculator will show $0.
📊 Kelly Bet Examples
| Bankroll | Odds | Probability | Edge | Full Kelly % | Half‑Kelly $ |
|---|---|---|---|---|---|
| $1,000 | +150 (2.50) | 45% | 12.5% | 5.0% | $25 |
| $5,000 | -110 (1.91) | 55% | 5.0% | 5.0% | $125 |
| $2,000 | +200 (3.00) | 40% | 20.0% | 10.0% | $100 |
| $10,000 | +100 (2.00) | 55% | 10.0% | 10.0% | $500 |
📍 Kelly Calculator by State
Personalized calculators considering state tax on winnings (affects net edge).
Florida
No state income tax
FL Kelly →Texas
No state income tax
TX Kelly →California
High state tax
CA Kelly →New York
High state tax
NY Kelly →New Jersey
State tax on winnings
NJ Kelly →🎰 Kelly Calculator by Sportsbook
Adjust for bookmaker limits and specific odds formats.
Bitstarz
Crypto sportsbook
Bitstarz →Bovada
American odds, high limits
Bovada →BetOnline
Decimal & American
BetOnline →Jackbit
Crypto sportsbook
Jackbit →⚙️ Advanced Features
📌 Real-World Examples
Example 1: NFL Underdog
Bankroll $2,000, odds +250 (3.50), estimated win probability 35%. Edge = 22.5%. Full Kelly = 9.6% of bankroll = $192. Half‑Kelly = $96.
Example 2: MLB Favorite
Bankroll $5,000, odds -150 (1.667), estimated probability 65%. Edge = 8.4%. Full Kelly = 13.4% = $670. Half‑Kelly = $335.
❓ Frequently Asked Questions
What is the Kelly Criterion?
A mathematical formula that determines the optimal size of a series of bets to maximize long-term growth, given your edge and the odds.
How do I estimate my probability of winning?
Use statistical models, historical data, or your own handicapping. For casino games with a known house edge, your probability is fixed (e.g., blackjack with basic strategy).
Why use half‑Kelly instead of full Kelly?
Full Kelly can be very volatile. Half‑Kelly reduces risk while still achieving about 75% of the growth. Most professional bettors use fractional Kelly.
What if the calculator shows 0?
That means you have no edge – the bet is not profitable. Only bet when edge > 0.
Can I use Kelly for casino games?
Yes, but only if you have an edge (e.g., card counting, bonus situations). For pure house edge games, Kelly recommends not betting.
How do I convert American odds to Decimal?
Positive: (odds/100)+1. Negative: (100/|odds|)+1. Our calculator does it automatically.
Is Kelly criterion used in investing?
Yes, it's also used for portfolio allocation. The same principles apply.
🔧 Related Tools
🧮 Mathematical Formula
f* = (bp - q) / b
Where:
- b = decimal odds – 1 (net odds received)
- p = probability of winning
- q = probability of losing = 1 – p
- f* = fraction of bankroll to bet
Our calculator uses this formula and also computes half‑Kelly (f*/2) and quarter‑Kelly (f*/4).
📋 Changelog
Mar 2, 2026 – Added support for American odds; improved edge display.
Feb 10, 2026 – Initial release of Kelly Criterion Calculator.
👨💻 Developed by Kevin Lee
Kevin Lee
Sportsbook Analyst · 6 yrs
Kevin has applied the Kelly Criterion to thousands of betting opportunities. His calculator is used by advantage players worldwide to optimize bet sizing and minimize risk.
Full Bio →Ready to Put Your Edge to Work?
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