What does −150 mean?

You must stake 150 to win 100. It marks a favourite: the shorter the price, the more you risk per unit of profit. +150 is the reverse — 100 stake wins 150.

Which format is best to compare prices in?

Decimal. It is a single multiplier, so the bigger number is always the better price. Comparing −140 with +120 across formats takes arithmetic; comparing 1.71 with 2.20 does not.

Does a higher implied probability mean I am more likely to win?

It means the price is shorter. It is the bookmaker's number with a margin built in, not an independent estimate, and it is not a forecast.

Betting Odds Calculator (American, Decimal & Fractional)

Convert odds formats, payout and implied probability.

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This converts odds formats and shows the payout arithmetic. It does not predict outcomes, and the implied probability includes the bookmaker's margin. No calculator gives you an edge. Betting is restricted by age and by state. If gambling is causing you harm, the National Problem Gambling Helpline is free, confidential and open 24/7: call or text 1-800-MY-RESET (1-800-697-3738), or chat at ncpgambling.org/chat.

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Formula

Decimal = American ÷ 100 + 1 when positive, or 100 ÷ |American| + 1 when negative. Profit = stake × (decimal − 1). Implied probability = 1 ÷ decimal

P(\text{implied}) = \frac{1}{\text{decimal}}

The three formats say the same thing differently. Decimal is the plainest: it is the multiplier on your stake including the stake back, so 2.50 turns 100 into 250. American odds say how much you win from 100 (+200) or how much you must stake to win 100 (−150). Fractional gives profit over stake. Implied probability is simply one divided by the decimal price.

Worked example

At −150 you must stake 150 to win 100, so a 100 stake wins 66.67 and returns 166.67. That is 1.6667 in decimal and 2/3 as a fraction, and it implies a 60% chance — though part of that 60% is the bookmaker's margin, not a real probability.

Where this can give the wrong answer

Implied probabilities across a market always total more than 100%. On a two-way market priced −110 each way they come to about 104.8%, and that 4.8% is the margin. It is why the implied figure is not the true chance.
There is nothing between −99 and +99 in American odds. Even money is +100, and the calculator rejects anything in the gap.
Fractional odds are shown to the nearest denominator bookmakers actually print, so a decimal price can come back as a fraction that is very slightly different.
American odds quote profit against 100, not a total return. +200 pays 200 profit on a 100 stake, returning 300.

FAQ

: You must stake 150 to win 100. It marks a favourite: the shorter the price, the more you risk per unit of profit. +150 is the reverse — 100 stake wins 150.

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