Understanding Betting Edges: A Guide for Tennis Bettors

What Is an Edge?

In sports betting, your edge is the difference between your estimated probability of an outcome and what the odds imply. If you believe a player has a 60% chance of winning, but the odds imply only 50%, you have a 10% edge.

The formula is simple:

Edge = Your Probability - Implied Probability

But getting it right requires careful attention to how odds work.

The Vig Trap

Bookmakers don't offer fair odds. They build in a margin called vig (or vigorish). Here's an example:

| | Player A | Player B | |---|---|---| | Decimal Odds | 1.90 | 1.90 | | Raw Implied Prob | 52.6% | 52.6% | | Total | 105.2% | — |

The probabilities sum to 105.2%, not 100%. That extra 5.2% is the vig — the bookmaker's guaranteed profit margin.

If you calculate edge using raw implied probabilities, you'll think you have a 2-3% edge that doesn't actually exist. At BreakPoint, we normalize for vig by dividing each probability by the overround:

• Normalized P(A) = 52.6% / 105.2% = 50.0%
• Normalized P(B) = 52.6% / 105.2% = 50.0%

Now the probabilities sum to 100%, and your edge calculation is accurate.

Sizing Your Bets: The Kelly Criterion

Once you've found a genuine edge, the next question is: how much should you bet?

The Kelly Criterion tells you the mathematically optimal stake:

Kelly % = (Edge) / (Odds - 1)

For example, with a 5% edge and decimal odds of 2.00:

Kelly % = 0.05 / (2.00 - 1) = 5% of bankroll

Most professional bettors use fractional Kelly (quarter or half Kelly) to reduce variance. At BreakPoint, our edge calculator shows both full and fractional Kelly recommendations.

Why Discipline Matters

Even with a genuine edge, short-term variance is enormous in tennis betting. A model with 55% accuracy will still lose 5-6 bets in a row regularly.

Key principles for long-term success:

• Never bet more than 3-5% of your bankroll on a single match
• Track every bet — our bet tracker calculates ROI, edge accuracy, and equity curves automatically
• Review your track record monthly — are your edges materializing?
• Be patient — 100+ bets is the minimum sample to evaluate performance

Edge Tiers at BreakPoint

We classify opportunities into tiers based on edge size:

| Edge | Classification | Recommendation | |------|---------------|----------------| | 4-6% | Standard edge | Consider betting | | 6-8% | Strong edge | Strong recommendation | | 8%+ | Premium edge | High-conviction play | | >10% | Suspicious | Likely stale data — skip |

The "suspicious" tier is important. Edges above 10% in efficient markets usually indicate stale odds, a model limitation, or missing information (like an injury). We flag these so you can investigate before betting.

Ready to find edges? Check out today's opportunities or calculate your own with the edge calculator.