Understand implied probability from American, decimal, and fractional odds so you can compare bookmaker pricing with your own projection and find value.
You see Lakers at +200 on DraftKings. That sounds like a good payout — but how likely does the sportsbook actually think the Lakers are to win? The answer is 33.3%, and that number is called implied probability.
Every time a sportsbook posts a line, it is putting a price tag on how likely it thinks an event is. Learning to read that price tag is the single most important skill in sports betting, because it lets you compare what the market believes against what you believe. When those two numbers disagree in your favor, you have found a potential value bet.
This guide covers the formulas for every major odds format, shows you how the vig inflates those numbers, and explains how to use implied probability to find edges.
Implied probability converts betting odds into a percentage. Think of it like a price tag at a store. If a sportsbook offers +200 on a team, the market is pricing that team's chance of winning at roughly 33.3%. The "implied" part means the probability is embedded inside the odds rather than stated outright.
The relationship is straightforward:
Implied probability does not tell you the true chance of an event happening. It tells you what the sportsbook's price assumes. The difference between implied probability and true probability is where profits and losses live over the long run.
Each odds format has its own conversion formula. The math is simple once you see it a few times.
Formula: Implied Probability = (1 / Decimal Odds) x 100
Decimal odds are the most intuitive format because they already represent your total return per unit staked.
Formula: Implied Probability = 100 / (American Odds + 100) x 100
Positive American odds show how much profit you would earn on a $100 stake.
Formula: Implied Probability = |American Odds| / (|American Odds| + 100) x 100
Negative American odds show how much you need to risk to profit $100.
Formula: Implied Probability = Denominator / (Denominator + Numerator) x 100
Fractional odds are popular in the UK. The numerator is potential profit and the denominator is your stake.
Use the Odds Converter to translate between formats instantly without manual math.
This table covers the most common betting odds and their implied probabilities. Bookmark it or use the Odds Converter for odds not listed here.
| American | Decimal | Fractional | Implied Probability |
|---|---|---|---|
| -300 | 1.33 | 1/3 | 75.00% |
| -200 | 1.50 | 1/2 | 66.67% |
| -150 | 1.67 | 2/3 | 60.00% |
| -130 | 1.77 | 10/13 | 56.52% |
| -110 | 1.91 | 10/11 | 52.38% |
| +100 | 2.00 | 1/1 | 50.00% |
| +150 | 2.50 | 3/2 | 40.00% |
| +200 | 3.00 | 2/1 | 33.33% |
| +300 | 4.00 | 3/1 | 25.00% |
| +500 | 6.00 | 5/1 | 16.67% |
If you add up the implied probabilities for both sides of a bet, you will almost always get a number higher than 100%. That extra amount is the vig (also called juice or vigorish). It is the sportsbook's built-in profit margin.
Consider the most common line in American sports betting: both sides priced at -110.
The sum is 104.76%, not 100%. That 4.76% above 100% is the overround — the vig expressed as a percentage of the total market. It means the sportsbook has built in a roughly 4.76% edge. No matter which side wins, the book collects more than it pays out over time.
The overround tells you how much the odds are inflated against bettors. A market with a 104.76% overround is more bettor-friendly than one with a 110% overround. Lower juice means the odds are closer to fair value, which makes it easier for skilled bettors to find edges.
Different bet types carry different vig levels. Moneylines and totals at major sportsbooks often sit around 104-105%. Parlays, props, and less liquid markets can carry significantly higher juice.
Since implied probability includes the vig, it overstates the chance of every outcome. To find the true (fair) probability, you need to strip out the juice.
The basic process:
For the -110 / -110 example:
Now the probabilities sum to 100%, and you have the market's true view of each outcome without the house edge baked in. The No-Vig Calculator handles this automatically for 2-way and 3-way markets.
Once you know the implied probability (or better, the fair no-vig probability), you can compare it against your own estimate. The gap between the two is your edge.
A sportsbook offers Team A at +150. That implies a 40% chance of winning.
Your analysis says Team A actually wins 48% of the time.
An 8-point gap is significant. Over many bets with this kind of edge, you would expect a positive return. Use the +EV Calculator to quantify the expected value in dollars for any specific wager.
Keep in mind: a single bet can still lose regardless of edge. Value betting is a long-run strategy. See the full breakdown in the value betting guide.
Even experienced bettors make mistakes with implied probability. Watch out for these:
An implied probability of 75% does not mean the outcome will happen. It means the market prices it as though it happens 75 out of 100 times. Underdogs win regularly. The implied probability is a pricing mechanism, not a prediction.
Comparing your estimate directly to raw implied probability (before removing the vig) makes every bet look slightly worse than it actually is. Always de-vig the odds first when evaluating edge. The fair probability from the No-Vig Calculator is the correct baseline for comparison.
The vig is distributed across all outcomes. Looking at only one side of the market gives you an incomplete picture. Always check both sides (or all sides in 3-way markets) and compute the total overround before drawing conclusions.
Odds move constantly. An implied probability calculated from yesterday's line may be meaningless today. Always use the current odds from your sportsbook when making decisions.
Tip: Bookmark the Odds Converter for quick conversions. When you are line shopping across 3-4 sportsbooks with different formats, being able to compare implied probabilities instantly is the difference between catching a mispriced line and missing it.
Open the Odds Converter and enter any odds from tonight's games. Watch the implied probability update in real time as you change formats. Then use the No-Vig Calculator to strip the juice and see the fair probability.
Implied probability is the win percentage suggested by the odds a sportsbook offers. It tells you how likely the market considers an outcome to be.
Divide 1 by the decimal odds, then multiply by 100. For example, decimal odds of 2.50 give an implied probability of 40%.
For negative odds, divide the absolute value by itself plus 100. For positive odds, divide 100 by the odds plus 100. Then multiply by 100 for a percentage.
The extra percentage above 100% is the vig (vigorish) — the sportsbook's built-in profit margin. A -110/-110 market totals 104.76%, meaning the book takes roughly 4.76% juice.
Compare the implied probability from the odds to your own estimated probability. If you believe the true chance is higher than what the odds imply, the bet may have positive expected value.
Implied probability includes the sportsbook's vig, so it overstates the chance of each outcome. True (or fair) probability is what you get after removing the vig, and it reflects the actual likelihood of the event.
Yes. Use the formula: denominator / (denominator + numerator) * 100. For example, 3/1 fractional odds give an implied probability of 25%.