Betting odds calculator.
Enter the odds in any format, American, decimal or fractional, plus your stake, and this free betting odds calculator shows your exact profit, your total payout, and the implied probability the price is pricing in. It converts every format both ways, so a +150 in New York and a 5/2 in London become the same bet. The guide below shows the formulas, the break-even win rate behind each price, and what the bookmaker margin quietly costs you.
Work out a bet
LiveFor fractional odds type them as 10/11 or 5/2. Stake is in any currency, the math is identical.
To win (profit)
90.91
total payout 190.91
Implied probability includes the bookmaker margin, so the real chances are a little lower. Calculations run in your browser; nothing you enter is stored. For entertainment, not betting advice.
The short answer
What is a betting odds calculator?
A betting odds calculator turns a price and a stake into real numbers: how much profit you would win, your total payout, and the implied probability the odds represent. It also converts between American, decimal and fractional odds, so you can compare any two prices on equal terms, whichever format a sportsbook shows.
How this calculator works
Pick the format your odds are in, type the price, and add your stake. The calculator converts the price to decimal odds internally, because decimal is the cleanest format to compute with, then works out the rest. Profit is your stake times the decimal odds minus one; total payout is your stake times the decimal odds; implied probability is one divided by the decimal odds.
A 100 stake at -110 returns 90.91 profit and a 190.91 payout, and the price implies a 52.38% chance. Change the format to fractional, type 10/11, and you get the identical result, because -110 and 10/11 are the same odds written two ways.
The three formats
American, decimal & fractional.
Three ways of writing the same thing. Each tells you the same two facts: how likely the bookmaker thinks the outcome is, and what it pays.
American odds
Built around 100. A positive price like +150 is the profit on a 100 stake. A negative price like -110 is the stake needed to win 100. Used mostly in the United States.
Decimal odds
The total return per unit staked, your stake included. 2.50 means a 1 stake returns 2.50. The global default across Europe, Australia and Canada, and the easiest to do the math with.
Fractional odds
Profit relative to stake. 5/2 wins 5 for every 2 staked. Traditional in the United Kingdom and Ireland. To get the payout, add the stake back: 5/2 returns 7 for every 2.
Side by side
Odds conversion table.
The same prices in all three formats, with the implied probability each one carries. Handy for converting in your head or sanity-checking the calculator.
| American | Decimal | Fractional | Implied probability |
|---|---|---|---|
| -1000 | 1.10 | 1/10 | 90.91% |
| -500 | 1.20 | 1/5 | 83.33% |
| -300 | 1.33 | 1/3 | 75.00% |
| -200 | 1.50 | 1/2 | 66.67% |
| -150 | 1.67 | 2/3 | 60.00% |
| -110 | 1.91 | 10/11 | 52.38% |
| +100 | 2.00 | 1/1 | 50.00% |
| +120 | 2.20 | 6/5 | 45.45% |
| +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% |
| +1000 | 11.00 | 10/1 | 9.09% |
The number nobody shows you
What win rate do you need to break even?
A price is also a target. To profit at given odds, your real win rate has to beat the implied probability. Most bettors never check this, which is why a -110 line feels like a coin flip when it actually demands you win 52.4% of the time.
| Odds (American) | Decimal | Win rate to break even |
|---|---|---|
| -200 | 1.50 | 66.67% |
| -150 | 1.67 | 60.00% |
| -110 | 1.91 | 52.38% |
| +100 | 2.00 | 50.00% |
| +150 | 2.50 | 40.00% |
| +200 | 3.00 | 33.33% |
The break-even win rate is just the implied probability of the price. Beat it over a large sample and you profit; fall short and you lose, however good the individual bets felt. This is the honest way to read a line, and weighing it against your own estimate of the chances turns it into a profit or loss per bet.
The hidden cost
What the margin really costs you.
When both sides of a market are priced at -110, the implied probabilities add up to more than 100%. That extra slice is the bookmaker margin, the vig, and it is where the house edge lives.
A standard spread is -110 on each side. Each side implies 52.38%, so the two add to 104.76%. The overround is that 4.76% above a fair 100%, and the hold, the share the book keeps, works out to 4.55%. Strip the margin out and both sides are really 50%, a true coin flip priced as if it were not.
That margin is not a one-off fee, it is charged on every bet. If you placed 100 bets of 100 each at -110 on genuine coin flips, you would expect to lose about 455, roughly 4.5 per bet, purely to the vig. Winning bettors do not beat the game, they beat the margin, by finding prices where their own probability is higher than the implied one.
It is also why line shopping matters. The same bet at -105 instead of -110 cuts your cost from about 4.5 to 2.4 per 100, so simply taking the better price more than halves what the margin takes. Stripping that margin out of a two-way market reveals the fair odds underneath, the book’s genuine estimate before its cut.
The formulas
No black box.
Here is the math.
Every conversion the calculator runs, written out. Decimal is the hub: get to decimal and everything else follows.
# American to decimal
pos: D = A / 100 + 1
neg: D = 1 + 100 / |A|
# Decimal to American
D ≥ 2: A = (D - 1) × 100
D < 2: A = -100 / (D - 1)
# Implied probability
P = 1 / D
# Payout from a stake S
profit = S × (D - 1)
payout = S × DThe point of it all
Does this bet have value?
A bet is worth making when your own estimate of the chances beats the implied probability in the price. That gap, not the size of the odds, is the entire game.
Convert the odds to an implied probability with the calculator. Then ask yourself, honestly, what you think the real chance is. If your estimate is higher than the implied probability, the price is in your favour and the bet is positive expected value. If it is lower, the bet is negative value no matter how tempting the payout looks.
Say a team is +150, an implied 40%. If you genuinely believe they win 50% of the time, the price is paying you for a 40% shot at something that happens 50% of the time, that is value. The same +150 when you only rate them a 30% chance is a bad bet wearing an attractive number. The Kelly criterion is one way to size the stake to the size of that edge.
How to convert betting odds by hand
Get the price into decimal odds. From a positive American price, divide it by 100 and add 1. From a negative price, divide 100 by the price without its sign and add 1. A fraction becomes top divided by bottom, plus 1.
For the implied probability, divide 1 by the decimal odds. Decimal 2.50 gives 0.40, a 40% chance.
For your profit, multiply your stake by the decimal odds minus 1. For the total payout, multiply your stake by the decimal odds.
To go back to American odds: if decimal is 2.00 or more, subtract 1 and multiply by 100. If it is under 2.00, divide -100 by the decimal minus 1.
Wherever you bet
Which odds format does your country use?
The same price looks different depending on where you are. This calculator reads and shows all three, so a price from any market is one click from the format you know.
United States: American odds
US sportsbooks default to American odds and the moneyline. Lines like -110 and +150 are the norm, and payouts are quoted in dollars.
UK & Ireland: fractional odds
British and Irish books traditionally show fractional odds like 5/2, though most now offer a decimal toggle. You will also hear margin called the overround, and the each-way market is common here.
Europe, Canada & Australia: decimal odds
Most of the rest of the world uses decimal odds, the cleanest format to read and compare. A price of 2.50 means a 1 stake returns 2.50, full stop.
Read the price right
Three mistakes to avoid.
The odds do not lie, but they are easy to misread. These three trip up most bettors.
Reading +200 as twice as likely
Bigger odds mean less likely, not more. A +200 price is an implied 33%, a +100 price is 50%. Long odds pay more precisely because the outcome is rated less probable, so a tempting number is a warning, not a bargain.
Forgetting the margin is baked in
Implied probability from a single price is always a little high, because the bookmaker margin is built into it. The two sides of a market add to more than 100%. To see the book’s genuine estimate, strip the margin out and compare the de-vigged numbers.
Chasing longshots for the payout
A 10/1 shot pays beautifully on the rare win, but it has to land about 1 time in 11 just to break even, and the margin on longshots is usually heavier than on short prices. The payout is real; so is the low chance behind it.
An honest word on expectations
Because the margin is charged on every bet, the maths favours the book over time, and most bettors finish behind. A calculator makes you sharper, not guaranteed: it helps you spot prices with value and avoid obviously bad ones, nothing more. Bet only what you can afford to lose, and if it stops being fun, free confidential help is at BeGambleAware.org.
Questions
Betting odds questions.
What is a betting odds calculator?
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It is a free tool that turns a price and a stake into your profit, your total payout and the implied probability behind the odds. It also converts between American, decimal and fractional formats, so you can compare any two prices on equal terms.
How do betting odds work?
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Odds do two things: they price how likely the bookmaker thinks an outcome is, and they set what it pays. Shorter odds mean a higher chance and a smaller payout; longer odds mean a lower chance and a bigger payout. The implied probability is one divided by the decimal odds.
What is the difference between American, decimal and fractional odds?
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They are three ways to write the same price. American odds centre on 100 and are used in the US. Decimal odds show the total return per unit staked and are the global standard. Fractional odds show profit over stake and are traditional in the UK and Ireland. -110, 1.91 and 10/11 are the same bet.
What is implied probability?
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It is the chance an outcome must have for the odds to be fair, found by dividing 1 by the decimal odds. Decimal 2.00 is 50%, and -110 is 52.38%. It always reads slightly high because the bookmaker margin is built into the price.
How much would I win on +150 or -110?
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A 100 stake at +150 wins 150 profit for a 250 payout. The same 100 at -110 wins 90.91 profit for a 190.91 payout. Profit is your stake times the decimal odds minus 1; payout is your stake times the decimal odds.
What is the vig (vigorish)?
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The vig is the bookmaker margin built into the odds, also called juice or the overround. On a -110 versus -110 market the two implied probabilities add to 104.76%, and that extra 4.76% is the margin. It is why both sides of a fair coin flip are not priced at +100.
How do I convert betting odds by hand?
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Get the price to decimal first: a positive American price divided by 100 plus 1, a negative price as 100 divided by its size plus 1, or a fraction as top over bottom plus 1. Then implied probability is 1 divided by the decimal, and payout is your stake times the decimal.
About the developer
Jean Borg
Jean builds and maintains every calculator on freecalculators.pro from Malta, with a focus on tools that are fast, free and show their working. This betting odds calculator uses the standard odds-conversion maths used across the industry and is provided for education and entertainment, not as betting advice. Please bet responsibly. Page last updated June 2026.