How to Remove Vig and Estimate Fair Odds

Question: How do I remove vig from sportsbook odds and estimate fair odds?

Plain-English Definition: What Does "Removing Vig" Mean?

When you look at betting odds from a sportsbook, the prices include a built-in margin called the "vig" (short for vigorish). This margin is how sportsbooks make money, ensuring that the total implied probability of all outcomes adds up to more than 100%. Removing the vig means stripping out this margin to estimate the "fair odds"—the odds you would get if there were no built-in profit for the sportsbook. These are also called "no-vig odds." They remain market-derived estimates, not known true probabilities.

How the Math or Process Works

To remove the vig from a two-way market (like a point spread or moneyline with two possible outcomes), you need to:

1. Convert each set of American odds to implied probability.
2. Add the implied probabilities together.
3. Divide each implied probability by the total from step 2. This normalizes the probabilities so they add up to 100%.
4. Convert the normalized probabilities back to odds. These are your no-vig or fair odds.

This process is called proportional no-vig normalization. It works for two-way and multi-way markets, but the Kingpin calculator is designed for two outcomes.

Step-by-Step Formula

• For positive American odds (e.g., +150): Implied Probability = 100 / (odds + 100)
• For negative American odds (e.g., -120): Implied Probability = absolute odds / (absolute odds + 100)
• Sum the two implied probabilities.
• For each outcome: No-Vig Probability = (Implied Probability) / (Sum of Implied Probabilities)
• Convert the no-vig probability back to American odds:
• If probability < 0.5: Odds = (100 / probability) - 100
• If probability >= 0.5: Odds = -100 / ((1 / probability) - 1)

Worked Example 1: Removing Vig from a Typical Two-Way Market

Suppose you see these odds for a basketball game:

• Team A: -110
• Team B: -110

Step 1: Convert to implied probabilities.

• Team A: 110 / (110 + 100) = 110 / 210 ≈ 0.5238 (52.38%)
• Team B: 110 / (110 + 100) = 110 / 210 ≈ 0.5238 (52.38%)

Step 2: Add the probabilities.

• 0.5238 + 0.5238 = 1.0476 (104.76%)

Step 3: Normalize each probability.

• Team A: 0.5238 / 1.0476 ≈ 0.5 (50%)
• Team B: 0.5238 / 1.0476 ≈ 0.5 (50%)

Step 4: Convert back to American odds.

• For 50% probability: (100 / 0.5) - 100 = 200 - 100 = +100

No-vig odds for both teams: +100

This means that if there were no vig, both sides would be priced at +100 (even money).

Worked Example 2: Removing Vig from Uneven Odds

Suppose you see these odds for a tennis match:

• Player X: -150
• Player Y: +130

Step 1: Convert to implied probabilities.

• Player X: 150 / (150 + 100) = 150 / 250 = 0.6 (60%)
• Player Y: 100 / (130 + 100) = 100 / 230 ≈ 0.4348 (43.48%)

Step 2: Add the probabilities.

• 0.6 + 0.4348 = 1.0348 (103.48%)

Step 3: Normalize each probability.

• Player X: 0.6 / 1.0348 ≈ 0.5796 (57.96%)
• Player Y: 0.4348 / 1.0348 ≈ 0.4204 (42.04%)

Step 4: Convert back to American odds.

• Player X (probability > 0.5): -100 / ((1 / 0.5796) - 1) ≈ -100 / (1.7246 - 1) ≈ -100 / 0.7246 ≈ -138
• Player Y (probability < 0.5): (100 / 0.4204) - 100 ≈ 238 - 100 = +138

No-vig odds:

• Player X: -138
• Player Y: +138

These are the estimated fair odds with the vig removed.

Common Mistakes and Limitations

• Confusing implied probability with true probability. The implied probability is a mathematical estimate based on market prices, not a guarantee or prediction of the actual chance of an outcome.
• Forgetting to normalize probabilities. Simply subtracting the vig or margin from each side does not produce fair odds. You must use proportional normalization so the probabilities add up to 100%.
• Applying the two-way formula to multi-way markets. The Kingpin calculator is designed for two outcomes. For markets with more than two outcomes, the math is similar but requires more steps.
• Assuming no-vig odds are always available. Sportsbooks rarely offer no-vig odds. These are theoretical prices for comparison or analysis.
• Using decimal or fractional odds incorrectly. The formulas above are for American odds. If you have decimal or fractional odds, convert them to American odds first.

How to Use the Kingpin No-Vig Odds Calculator

The Kingpin no-vig odds calculator helps you remove the vig from any two-way market. Here’s how to use it:

1. Find the American odds for both sides of your bet (e.g., -120 and +110).
2. Enter each set of odds into the calculator fields.
3. Select Calculate to process the math.
4. The calculator will display the no-vig probabilities and the corresponding fair odds for both outcomes.

This tool is useful for comparing sportsbook prices, evaluating value, or understanding how much margin is built into a market. Remember, the calculator works for two-way markets only.

Responsible Betting and Final Tips

• Use no-vig odds for analysis, not as a prediction. No-vig odds are a mathematical estimate based on current market prices, not a guarantee of outcome or a prediction of what will happen.
• Never bet more than you can afford to lose. Removing the vig helps you understand pricing, but it does not guarantee profit or winning bets.
• Check your math and use reliable tools. Manual calculations can lead to mistakes. Double-check your work or use the Kingpin calculator for accuracy.
• Be aware of market changes. Odds can move quickly. The no-vig odds you calculate are only as current as the prices you enter.
• Seek help if you have concerns about your betting. Responsible gambling means setting limits and knowing when to take a break.

Understanding how to remove vig and estimate fair odds is a valuable skill for any sports bettor. It helps you compare the normalized market prices and make more informed decisions. Always use these tools and concepts responsibly.

Use the Kingpin calculator

Run your own numbers with the related Kingpin betting calculator. The tool applies the formulas described above and does not predict winners.

Bet responsibly

Sports betting involves risk. Never risk money you cannot afford to lose, never chase losses, and set firm time and spending limits. If gambling stops being fun, visit the National Council on Problem Gambling for help.