Bankroll Calculator
Calculate optimal bet sizes, track ROI, and manage your sports betting bankroll like a professional.
Unit Size Calculator
Determine your standard bet size based on your total bankroll. Most professionals use 1-3% per bet.
Kelly Criterion Calculator
Calculate mathematically optimal bet size based on your edge and the odds offered.
ROI Calculator
Calculate your return on investment based on your betting history.
Break-Even Calculator
Find the win percentage needed to break even at any given odds.
Quick Unit Reference
| Bankroll | 1% Unit | 2% Unit | 3% Unit | 5% Unit |
|---|---|---|---|---|
| $500 | $5 | $10 | $15 | $25 |
| $1,000 | $10 | $20 | $30 | $50 |
| $2,500 | $25 | $50 | $75 | $125 |
| $5,000 | $50 | $100 | $150 | $250 |
| $10,000 | $100 | $200 | $300 | $500 |
Understanding the Kelly Criterion
The Kelly Criterion is a mathematical formula that determines the optimal bet size to maximize long-term growth while minimizing the risk of ruin. It was developed by John Kelly at Bell Labs in 1956.
b = decimal odds - 1 | p = win probability | q = loss probability (1 - p)
Why Kelly Matters
Betting too much of your bankroll on any single bet exposes you to unnecessary risk. Betting too little leaves money on the table. Kelly finds the sweet spot - the exact amount that maximizes your expected growth rate.
Pro Tip: Use Fractional Kelly
Most professional bettors use "half Kelly" or "quarter Kelly" - betting 25-50% of what the Kelly formula suggests. This reduces volatility while still capturing most of the expected growth. Full Kelly can lead to large drawdowns that are psychologically difficult to handle.
When Kelly Doesn't Apply
The Kelly Criterion assumes you know your true edge - but in sports betting, this is nearly impossible to calculate precisely. Use Kelly as a guide, not gospel. If you're unsure about your edge, flat betting (same amount on every bet) is a safer approach.
Critical Warning: Edge Estimation
If you overestimate your edge, Kelly will tell you to bet too much. If you think you have a 55% win rate but you actually have 50%, Kelly could lead you to ruin. Always be conservative in your edge estimates.
Bankroll Management Principles
The Golden Rules
Professional sports bettors follow strict bankroll management rules. These aren't suggestions - they're the difference between long-term success and going broke.
- Never bet more than 5% on a single game - Even your strongest plays should be capped
- Don't chase losses - Increasing bet sizes after losses is a path to ruin
- Track every bet - You can't improve what you don't measure
- Reassess unit size monthly - As your bankroll grows or shrinks, adjust
- Separate gambling money from living expenses - Only bet what you can afford to lose
The 1-3-5 Unit System
Many handicappers use a tiered confidence system:
- 1 Unit: Standard plays - slight edge identified
- 3 Units: Strong plays - clear edge with multiple supporting factors
- 5 Units: Max plays - only 1-2 per month, very high confidence
Variance is Real
Even a 55% bettor will experience 10+ game losing streaks. Your bankroll needs to survive these inevitable downswings. At 2% units, a 10-game losing streak only costs 20% of your bankroll - painful but survivable. At 10% units, you're down 65% and likely out of the game.