How esports betting odds work: decimal, fractional, American and implied probability

Esports betting odds tell you two things at once: how much a winning bet pays and what probability the bookmaker is pricing in. Decimal odds of 2.50 pay 2.50 units in total for every 1 unit staked, and imply a probability of 1 ÷ 2.50 = 40%.

The same price can be written three ways: decimal (2.50), fractional (3/2) or American (+150). Which one you see depends on the site and your region, but the maths underneath is identical. This guide shows how to read each format, how to convert between them and how to turn any price into an implied probability.

All matches and prices below are fictional and used only to explain the arithmetic.

Decimal odds: the total return per unit

Decimal odds are the most common format on esports betting sites and the easiest to work with. The number is the total amount you get back for each unit staked, including your stake.

Total return = stake × decimal odds
Profit       = stake × (decimal odds − 1)

Worked example (fictional): you stake 10 units on a team priced at 2.50.

• Total return if it wins: 10 × 2.50 = 25 units
• Profit: 10 × 1.50 = 15 units
• If it loses: you lose the 10 units staked.

A price of exactly 2.00 is "even money": you double your stake if you win. Anything below 2.00 is a favourite's price (profit smaller than the stake). Anything above 2.00 pays a profit larger than the stake.

Fractional odds: profit over stake

Fractional odds are traditional in the UK and Ireland. The fraction is profit ÷ stake. At 3/2 you win 3 units of profit for every 2 staked.

To convert fractional to decimal, divide the fraction and add 1:

decimal = (numerator ÷ denominator) + 1
7/4  →  1.75 + 1 = 2.75

To go the other way, subtract 1 from the decimal and write it as a fraction. 1.91 becomes 0.91, which is 91/100. Sites usually round awkward fractions like that to a familiar one such as 10/11, so the fractional price you see may be slightly different from the exact decimal.

American odds: plus and minus

American (moneyline) odds use a sign to tell you which side of even money you're on.

• Positive (+150): the profit on a 100-unit stake. +150 means stake 100 to win 150 profit.
• Negative (−150): the stake needed to win 100 profit. −150 means stake 150 to win 100 profit.

Conversions to decimal:

positive:  decimal = 1 + (American ÷ 100)     +240 → 1 + 2.40 = 3.40
negative:  decimal = 1 + (100 ÷ |American|)   −150 → 1 + 0.667 = 1.67

From decimal back to American: if the decimal is 2.00 or more, American = (decimal − 1) × 100, written with a plus. If it's below 2.00, American = −100 ÷ (decimal − 1).

Conversion table

Every row below was computed in Python from the decimal price. Implied probability is 1 ÷ decimal, rounded to two decimal places.

Two patterns are worth remembering. The shorter the price, the higher the implied probability. And the jump in probability between neighbouring prices is much bigger at the short end: moving from 1.25 to 1.50 changes the implied chance by more than 13 percentage points, while moving from 4.00 to 6.00 changes it by about 8.

Implied probability: what the price is saying

The implied probability of a price is the break-even win rate for that price. If a bet at 2.50 wins exactly 40% of the time, you break even over the long run before any margin. Win it more often and the price was generous; win it less often and it was poor.

implied probability = 1 ÷ decimal odds
2.50 → 1 ÷ 2.50 = 0.40 = 40%
1.62 → 1 ÷ 1.62 = 0.6173 = 61.73%

Here is a fictional best-of-three match to show the idea on a full market:

The two implied probabilities add up to 105.21%, not 100%. A match can only have one winner, so real probabilities must add to exactly 100%. The extra 5.21 percentage points is the bookmaker's margin, also called the overround. It's how the price is built so the bookmaker expects to profit whichever side wins. Our guide to bookmaker margin shows how to measure it and remove it to estimate the "fair" price.

That's why implied probability is the bookmaker's number, not the truth. It's a useful way to compare prices, but it always contains a slice of margin.

Worked conversion checklist

Use this sequence whenever you see a price in an unfamiliar format:

• Convert it to decimal first (fractional: divide and add 1; American: use the plus or minus formula).
• Multiply your stake by the decimal to get the total return, and subtract the stake to get profit.
• Divide 1 by the decimal to get the implied probability.
• Add up the implied probabilities for every outcome in the market to see the margin.
• Ask whether you'd still be comfortable if the stake were lost, because most of the time some bets will be.

What odds do not tell you

A price is not a prediction you can rely on, and it isn't a promise. Some things odds don't show:

• Settlement rules. Whether a match-winner bet includes overtime, what happens if a map is forfeited and how a substitute player affects a bet all depend on the site's rules. Read them before betting.
• How the price will move. Odds change as money comes in, and late roster news can move a price sharply. The price you took is the one that counts.
• Whether you have an edge. To profit over time you'd need to estimate probabilities better than the market, consistently, after the margin. Most bettors don't, and a few good results aren't evidence that you do.

Different markets also use the same formats. The odds on a map handicap or a total rounds line are read exactly the same way as the match winner; only what the bet settles on is different. See esports market types for how each one works.

Quick reference

Decimal → probability:   1 / d
Fractional a/b → decimal: a/b + 1
American +A → decimal:   1 + A/100
American −A → decimal:   1 + 100/A
Return = stake × d       Profit = stake × (d − 1)

If you remember one thing, make it this: convert to decimal, then to implied probability. Everything else on this site — margin, markets, staking — builds on that single step. Before you put money on any of it, read our bankroll guide and set a limit you can live with.