Every price is a percentage in disguise.
Odds look like a payout instruction, and they are, but they are also a statement about how often something has to happen. Convert -110 and it says 52.38 percent. Convert +200 and it says 33.33 percent. That figure is the exact win rate the price demands before it gives anything back, which is the threshold any opinion has to clear. This page covers both formulas, the full ladder of common prices, and the two places the number quietly misleads people.
Implied probability is the break-even rate
Implied probability is the win rate a price demands before it returns anything at all. Two formulas cover every American price. For a negative price, drop the minus sign and divide the number by itself plus 100, so a football favorite at -200 is 200 divided by 300, or 66.67 percent. For a positive price, divide 100 by the price plus 100, so a baseball underdog at +200 is 100 divided by 300, or 33.33 percent. Those two happen to sum to exactly 100, which is what a market with no margin in it would look like.
That same figure has a second name. Ask how often you must be right at -200 before you stop losing money and the answer is also 66.67 percent, because a price that pays your risk back over the long run is by definition a price quoting your win rate. Implied probability and break-even percentage are one number reached from two directions, one from the book's side and one from yours, which is why the two terms get used interchangeably.
From -300 down to +500
Start at the short end. A price of -300 demands 75 percent, because 300 divided by 400 is three quarters. A price of -200 demands 66.67 percent, and -150 demands 60 percent. The standard -110 that sits on NFL sides and totals demands 52.38 percent, not the 50 percent most people assume. Even money at +100 demands exactly 50 percent. Past that the ladder runs the other way: +150 demands 40 percent, +200 demands 33.33 percent, and a +500 futures price demands 16.67 percent.
Those eight numbers are the whole of what a price is telling you. A -200 quote demands 66.67 percent whether it sits on an NBA moneyline, an NFL first-half line, or a baseball run line, and it says nothing whatsoever about the teams involved. That is why the conversion has to happen before any comparison rather than after it. Your own view of a game is already a percentage, whether or not you have ever written it down, so the price has to become one too before the two can be set beside each other.
The long end is worth checking by hand, because it is the rung people misread most often. A +500 price pays five to one, so it breaks even at one win in six, and one in six is 16.67 percent. Six one-unit wagers at that price cost six units, and the single winner returns five units of profit plus the unit you staked, which is exactly six back. Nothing is won and nothing is lost, and that is what a break-even rate looks like when you count it out.
The two ways the number misleads
The first trap is treating one implied probability as what the market actually thinks. It cannot be, because the sportsbook's margin is folded into the number before you ever see it. Two sides of an NBA spread at -110 imply 52.38 percent each, which is 104.76 percent between them, and no matchup can be 104.76 percent likely to resolve. Pulling that surplus back out is a separate job, explained in what is juice and done for any pair of prices by the no-vig calculator.
The second trap is quieter and costs more, because it looks like a check that has already been done. A converted percentage is a statement about the price and nothing else, so it is blind to whatever the price is attached to. A football side laying 3 points at -110 and the same side laying 3.5 at -110 both convert to 52.38 percent, and so does an over on a basketball total of 219.5 at -110 and an over on the same game at 221.5. The arithmetic never looks past the digits after the sign, so it cannot tell you that one version of each pair is materially worse, and a record that stores the percentage without the line has stored prices rather than bets.
Both traps come from the same place. The conversion is an exact statement about a price, and every question a bettor actually has is about more than the price. Two converted percentages are worth comparing only when the line underneath them matches, and a single one is worth something only when it is set beside an estimate of your own. The scale is not linear either, so ten cents of price buys very different amounts of probability depending on where on the board it lands, which how to read betting odds works out in full.
Write your estimate down before you convert
The order of operations matters more than it sounds. Convert the price first and the book's figure becomes the anchor that every later thought gets measured against, which is precisely the number you were trying to test. Say what you think the chance is, in plain percentage terms, commit to it, and only then look at what the price is asking for.
Then compare the two and be honest about the size of the gap. Suppose an NBA side looks like a genuine 60 percent to you. At -150 the price demands exactly 60 percent, so there is no bet there, only your own opinion handed back with nothing attached to it. At -120 the demand falls to 54.55 percent and the same opinion carries 5.45 percentage points of edge. At -200, which demands 66.67 percent, the identical read is a losing wager, and it stays a losing wager on the nights it happens to cash.
Round your estimate to something you would defend out loud. A model can carry a decimal place, a judgement call cannot, and a 54.3 percent that was really nothing more than a hunch will manufacture edges that were never there. If the gap between your number and the price is smaller than your own uncertainty, treat it as no gap at all. The break-even calculator does the conversion for you, and positive expected value turns the gap into a number you can actually stake against.
A correct bet that loses is still correct
This is where writing your own number down earns its keep a second time. A bettor who only ever saw the book's percentage has nothing to consult when the results turn, so every loss reads as evidence that the read was wrong, even though a wager you correctly assessed at 55 percent still loses nearly half the time. Having your estimate on paper turns that into a question with an answer, whether the number was wrong or the sample was short, and it is the difference between reviewing a bad week and reacting to one. If the next stake is being decided by how much is down rather than by what the numbers say, the material on responsible gambling is worth reading before the next slate rather than after it.
Implied probability, answered
What is implied probability in betting?
Implied probability is the win rate a betting price demands before it returns anything over the long run. It is calculated from the odds alone, so it describes the price rather than the game being played. Because it is also the point at which a wager stops losing money, it is the same number as the break-even percentage for that price.
How do you calculate implied probability from American odds?
There are two formulas, one for each sign. Drop the minus from a negative price and divide the number by itself plus 100, so -200 becomes 200 divided by 300, which is 66.67 percent. For a positive price, divide 100 by the price plus 100, so +200 becomes 100 divided by 300, which is 33.33 percent. Both return the same quantity, which is the share of the time that price has to win before it pays for itself.
Is implied probability the same as the true probability?
Implied probability is an exact fact about the price rather than a forecast of the event, and it sits above the market's own no-vig estimate, because the sportsbook's margin is folded inside it before you ever see the number, and whether it also sits above the true chance is the entire question a bettor is trying to answer. What it defines precisely is the threshold your wager has to clear at that price, which is useful in a way a forecast is not. A bettor who reads the two as one number has quietly adopted the price as an opinion instead of testing one against it.
What does break-even percentage mean?
Break-even percentage is how often a wager has to win before it stops losing money at the price you took. A +150 underdog needs to land 40 percent of the time, so a bettor hitting those at 45 percent is profitable and one hitting them at 35 percent is not. It is the same figure as the implied probability of the price, approached from the bettor's side rather than the book's.
How do you convert a probability into American odds?
Run the two formulas backwards. Take your estimate and what is left of 100, divide the larger by the smaller, multiply by 100, and attach a minus sign if your estimate sits above 50 percent or a plus sign if it sits below. An estimate of 40 percent gives 60 divided by 40, times 100, which is +150, and an estimate of 75 percent gives 75 divided by 25, times 100, which is -300. Converting in this direction turns an opinion into the shortest price you would accept for it.
What is the implied probability of +200?
A price of +200 implies 33.33 percent, because 100 divided by 300 is one third. In practical terms it is a price that only pays for itself if it wins about a third of the time, and anything above that rate is profit. The same arithmetic makes +500 a 16.67 percent proposition, which is a price that pays for itself at one win in six.
What price do I need if I think something happens 60 percent of the time?
A price of -150 implies exactly 60 percent, so it hands you nothing at all. It simply quotes your own opinion back at you. To have a bet you need a longer price than -150, and at -120 the demand drops to 54.55 percent, which leaves 5.45 percentage points of edge. Anything shorter, such as -200 at 66.67 percent, is a losing wager even though your read on the game is correct.
Does implied probability change when the line moves?
It changes every time the price changes, because it is calculated from the price and nothing else. A side that drifts from -110 to -120 has raised its demand from 52.38 percent to 54.55 percent, so an opinion formed an hour ago is worth less against the new number. A move in the handicap alone, from 3 points to 3.5 at the same -110, leaves the figure untouched even though the wager has got harder. This is why the price you took matters as much as the side you took, and why two people backing the same team can hold very different bets.
Know the number behind the price
Every market we track is converted to a percentage and set beside our own estimate of the same outcome, so the only comparison that decides a bet is already on the screen.