Converting odds to a percentage means turning a betting price into its implied probability, the win chance baked into the number. A price of -150 is a 60% chance. A price of +200 is a 33.3% chance. The math is quick once you know the formula for each odds format, and it is the single most useful skill for reading a line, because a percentage tells you exactly what the price is asking you to believe. You can convert any price in a second with the free betting odds converter, and this guide shows the math behind it so you can do it in your head.
The formulas: odds to percentage in every format
Odds come in three formats, and each has a clean formula that returns the implied probability as a percentage. Learn these three lines and you can convert any price you see.
American odds to percentage
American odds split into negative (favorites) and positive (underdogs), so there are two versions:
- Negative odds: percentage = |odds| / (|odds| + 100). The bars mean you drop the minus sign first. So -150 becomes 150 / (150 + 100) = 150 / 250 = 0.60, or 60%.
- Positive odds: percentage = 100 / (odds + 100). So +200 becomes 100 / (200 + 100) = 100 / 300 = 0.333, or 33.3%.
If American odds are the format you see most, the American odds guide breaks down how the plus and minus prices read before you ever convert them.
Decimal odds to percentage
Decimal is the easiest format of all. The percentage is just 1 divided by the decimal price: percentage = 1 / decimal. A price of 2.50 becomes 1 / 2.50 = 0.40, or 40%. A price of 1.54 becomes 1 / 1.54 = 0.649, or about 65%. One division and you are done.
Fractional odds to percentage
For a fractional price written as numerator/denominator, the formula is denominator / (numerator + denominator). A price of 5/2 becomes 2 / (5 + 2) = 2 / 7 = 0.286, or 28.6%. A price of 4/7 becomes 7 / (4 + 7) = 7 / 11 = 0.636, or about 64%. Fractional odds are common in horse racing and UK markets, and this formula handles both the odds-against (5/2) and odds-on (4/7) cases.
Four worked examples
Here are the four formats run through their formulas, with the arithmetic shown so you can check your own:
- -150 (American favorite): 150 / (150 + 100) = 150 / 250 = 60%.
- +200 (American underdog): 100 / (200 + 100) = 100 / 300 = 33.3%.
- 2.50 (decimal): 1 / 2.50 = 40%.
- 5/2 (fractional): 2 / (5 + 2) = 2 / 7 = 28.6%.
Want the reverse, turning a percentage back into a fair price? The implied probability calculator goes both directions, so you can enter 60% and get the fair odds that match it.
Why converting to a percentage matters
A raw price like -150 is hard to judge. A percentage is not. Once you know -150 means 60%, you can hold that number against your own read: if you think the favorite wins closer to 70% of the time, the price is offering you more than it should, and that gap is where a value bet lives. Converting to a percentage is the first honest step, because it forces the price into the same units as your own opinion.
There is a catch worth understanding. Add up the implied percentages on both sides of a market and they total more than 100%. Take a standard -110 / -110 line: each side converts to 110 / 210 = 52.4%, and the two sides sum to 104.8%. That extra 4.8% is the margin, the built-in fee. Strip it out by dividing each side by the total (52.4 / 104.8 = 50%) and you get the true probability the market actually implies, which is 50% each. The gap between the posted percentage and the true percentage is exactly what a house margin costs you. On BettorEdge you take prices peer to peer at community odds with no built-in margin, so the percentage you convert is much closer to the true one.
Prediction market prices are already percentages
If you have traded on a prediction market, you have already been doing this conversion without the formula. A prediction market contract priced at 65 cents is simply a 65% implied probability, because the contract pays out one dollar if it hits. There is no odds format to decode: the price is the percentage. So a bettor moving between prediction-market prices and sportsbook-style odds is doing one conversion in both directions, cents to percentage one way, American or decimal odds to percentage the other. Learn the formulas above and both worlds read the same. For a deeper look at that bridge, see our guide on prediction market odds to percentage.
Ready to put a converted price to work? Sign up on BettorEdge and bet peer to peer at community odds, so the percentage you calculate is the real one, not a number padded with house margin.
Odds to percentage FAQ
How do you convert odds to a percentage?
Use the formula for the odds format. For decimal odds, divide 1 by the price. For negative American odds, divide the odds (without the minus) by the odds plus 100. For positive American odds, divide 100 by the odds plus 100. For fractional odds, divide the denominator by the numerator plus the denominator. Each returns the implied probability as a percentage.
What is -110 as a percentage?
-110 American odds convert to about 52.4%. The math is 110 / (110 + 100) = 110 / 210 = 0.524. This is the classic standard-juice price on a point spread, and it is why two -110 sides add up to roughly 104.8% rather than a clean 100%.
What is +150 as a percentage?
+150 American odds convert to 40%. The math is 100 / (150 + 100) = 100 / 250 = 0.40. In decimal that same price is 2.50, and 1 / 2.50 also equals 40%, so both formats agree.
Why do the percentages add up to more than 100%?
Because the price includes a margin. When you convert both sides of a market and they total more than 100%, the excess is the built-in fee. Divide each side by that total to remove the margin and reveal the true probability, which sums to exactly 100%.
What does the percentage actually tell me?
It is the break-even win rate. A price that implies 60% needs the outcome to happen more than 60% of the time to profit long term. If your own estimate of the real chance is higher than the implied percentage, the bet has positive expected value.
Is odds to percentage the same as implied probability?
Yes. Converting odds to a percentage and calculating implied probability are the same operation with the same formulas. Implied probability is just the technical term for the win percentage a price represents.
Convert odds to a percentage
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