Fractional to decimal
decimal = a ÷ b + 1
6/4 → 1.5 + 1 = 2.50
Add 1 to include your stake.
Guides · Betting odds
Esports betting odds explained: formats, probability and margin
Odds are a price and a probability at once. Decimal odds of 2.00 return $20 on a $10 stake and say the bookmaker rates the chance at 50% at most. Divide 1 by the odds for both teams, add them up, and the part above 100% is what the bookmaker keeps.
This guide converts between the odds formats esports sites use, works out the margin on an example CS2 match, and shows what is different in esports: series length, map handicaps and map totals.
Example odds, not live
Margin calculator
18+ only
By
Liam Fletcher
Updated Oct 8, 2026
Short answer
How do I turn esports odds into a probability?
Divide 1 by the decimal odds. Vitality at 1.62 gives 61.7% and Falcons at 2.30 gives 43.5%. Together that is 105.2%; the part above 100% is the bookmaker's mark-up, a margin of 4.9% at GG.bet in our example.
Vitality 1.62
61.7%
1 ÷ 1.62
Falcons 2.30
43.5%
1 ÷ 2.30
Sum
105.2%
GG.bet, example
Margin
4.9%
1 − 1 ÷ sum
Esports odds in six numbers
-
1 ÷ odds
Gives the chance the price implies. Odds of 4.00 mean 25%.
-
5.3%
Average margin across ten bookmakers on the same example CS2 match.
-
2.5%
The margin left if you take the best price on each team from different sites.
-
64.8%
How often a team that wins 60% of maps wins a best-of-three. In a best-of-one it is 60%.
-
2.78
Fair odds for −1.5 maps when a team wins 60% of maps: it must win 2–0, a 36% chance.
-
$51
Extra cost per $1,000 staked at the dearest site in the example compared with the cheapest.
Odds formats
The same odds in decimal, fractional and American
Decimal odds are standard on esports sites. UK-facing books also show fractions and US-facing books American odds. The format never changes the price.
Same bet, three ways to write it. 2.00, 1/1 and +100 all pay $200 back on a $100 stake.
| Decimal | Fractional | American | Probability | Payout on $100 | Win on $100 | What it means |
|---|---|---|---|---|---|---|
| 1.25 | 1/4 | −400 | 80.0% | $125 | $25 | heavy favourite, common for a tier-1 team against tier-2 |
| 1.50 | 1/2 | −200 | 66.7% | $150 | $50 | clear favourite |
| 1.80 | 4/5 | −125 | 55.6% | $180 | $80 | a common minimum odds in bonus terms |
| 2.00 | 1/1 | +100 | 50.0% | $200 | $100 | even money |
| 2.50 | 6/4 | +150 | 40.0% | $250 | $150 | slight underdog |
| 3.00 | 2/1 | +200 | 33.3% | $300 | $200 | wins about one time in three |
| 5.00 | 4/1 | +400 | 20.0% | $500 | $400 | an upset, about one time in five |
Converting
How to convert between odds formats
American to decimal
+A: A ÷ 100 + 1
−A: 100 ÷ A + 1
−125 → 1.80
Plus shows the win on $100; minus shows what you stake to win $100.
Decimal to probability
chance = 1 ÷ decimal
1.80 → 55.6%
This chance includes the margin, so it is a little too high.
Hong Kong to decimal
decimal = HK + 1
1.50 HK → 2.50
Hong Kong odds show the profit only, as many Asian-facing books print them.
Margin Example odds
Find the margin on any esports match
Use GG.bet's example odds, or type in any two or three prices.
| Outcome | Odds (GG.bet, example) | 1 ÷ odds | Fair odds |
|---|---|---|---|
| Vitality | 1.62 | 61.7% | 1.70 |
| Falcons | 2.30 | 43.5% | 2.42 |
| Sum | 105.2% | 100.0% |
Three steps
- Work out 1 ÷ odds for each side and add them: 105.2%.
- Margin = 1 − 1 ÷ sum: 4.9%.
- Fair odds = odds × sum: Vitality 1.70, Falcons 2.42.
What it means: on every $1,000 staked on this market the book keeps about $49 on average.
Esports specifics
Three things that make esports odds different
A team's chance per map decides its price for the whole series. These examples assume each map is independent.
-
Series length
A team that wins 60% of maps wins a best-of-one 60% of the time, a best-of-three 64.8% and a best-of-five 68.3%. Fair series odds fall from 1.67 to 1.54 to 1.46. Group stages often use best-of-one, where upsets are more common.
-
Map handicap −1.5
In a best-of-three, −1.5 maps needs a 2–0 win: the per-map chance squared. At 60% per map that is 36%, fair odds 2.78; at 70% it is 49%, fair odds 2.04. The opponent's +1.5 is the other side: 64% at 60%.
-
Total maps over 2.5
A best-of-three goes to a third map when the first two are split. At 60% per map the chance is 2 × 0.6 × 0.4 = 48%, fair odds 2.08; between two even teams it is 50%. The closer the teams, the more likely over 2.5.
Pure probability maths, no bookmaker data.
Compare odds Example odds
Same match, ten prices
CS2 · example match
Example odds · not live
Vitality
BO3
Match winner
Falcons
| Bookmaker | Vitality | Falcons | Margin | Payout |
|---|---|---|---|---|
| GG.bet | 1.62 | 2.30 | 4.9% | 95.1% |
| ThunderPick | 1.64 | 2.28 | 4.6% | 95.4% |
| 1xBet | 1.65 | 2.31 | 3.7% | 96.3% |
| BC.GAME | 1.67 | 2.30 | 3.2% | 96.8% |
| Stake.com | 1.63 | 2.34 | 3.9% | 96.1% |
| Betsson | 1.60 | 2.22 | 7.0% | 93.0% |
| Parimatch | 1.62 | 2.24 | 6.0% | 94.0% |
| 22BET | 1.64 | 2.27 | 4.8% | 95.2% |
| 20bet | 1.60 | 2.26 | 6.3% | 93.7% |
| 1win | 1.56 | 2.22 | 8.4% | 91.6% |
| Best odds per outcome | 1.67 | 2.34 | 2.5% | 97.5% |
Example odds set by the editors, not live prices.
How to read the table
Each row is one bookmaker's example price on the same CS2 match. The best price per team is highlighted; the margin column runs from green (cheapest) to red (dearest).
What it means: BC.GAME keeps 3.2% and 1win 8.4%. Taking the best price on each side cuts the margin to 2.5%.
Patterns & exceptions Example oddsExample data
What decides the price you get
Same match, different margin
What it means: on $5,000 a year in stakes the gap between the cheapest and dearest site in the example is $257.
Exception: a site with a higher margin can still have the best price on one team, as Stake.com does on Falcons here.
Margins multiply across legs
What it means: five 5% legs cost you 22.6% of the stake on average, against 5% on a single.
Exception: an accumulator boost can cover part of that cost; check the boost against the extra margin.
Responsible gambling
Bet only if you are 18+ and it stays fun
Esports fans are young
Licensed sites check age and ID before you can withdraw. If you are under 18, or under the legal age where you live, this site is for information only.
Our responsible gaming policySet a limit before the first deposit
Decide what a month of betting may cost and set a deposit limit in your account. Never top up to chase a loss.
Gambling addiction helpFree help, worldwide
If betting stops being fun, talk to someone. Gambling Therapy runs free, confidential support online in many languages.
Gambling TherapyGlossary
Odds terms in one place
- Implied probability
- The chance a price stands for: 1 ÷ decimal odds. So what: compare it with your own estimate before you bet.
- Margin (vig, juice)
- The share of stakes the book keeps: 1 − 1 ÷ sum of implied chances. So what: lower margin, more back on average.
- Overround
- The sum of implied chances above 100%, e.g. 105.2%. So what: the same mark-up as the margin, written differently.
- Fair odds
- Odds with the margin removed: odds × sum. So what: the price a bet would have with no mark-up.
- Map handicap
- A team starts with a map deficit or lead, e.g. −1.5 maps. So what: turns a short favourite into a longer price.
- Line shopping
- Taking the best price for your pick across several sites. So what: the easiest way to lower what each bet costs.
Esports odds FAQ
How are esports betting odds set?
Traders start from a probability for each team (form, map pool, roster, patch) and add a margin. Prices then move with the money bet and with news such as stand-ins. That is why the same match is priced differently at different sites.
Which odds format is best for esports betting?
Decimal. It includes the stake, so 1 ÷ odds gives the implied chance directly. Every format pays the same; see the conversion table above.
How do I calculate winnings from decimal odds?
Multiply stake by odds. $20 at 1.75 returns $35, which is $15 profit plus your $20 stake.
Why do odds differ between esports betting sites?
Each site sets its own margin and reacts to its own customers' bets. On our example match the margin runs from 3.2% to 8.4%. Compare prices on our CS2 betting and Dota 2 betting pages.
What is a good margin on an esports match?
On a two-way match winner market, under 5% is competitive. Props, live markets and lower-tier matches usually carry more. Work it out with the calculator above before you bet.
Are favourites safer in a best-of-three?
Yes, a little. A team that wins 60% of maps wins 64.8% of best-of-threes, against 60% of best-of-ones. Short odds in a best-of-one carry more upset risk.
What does −1.5 maps mean?
The team must win the best-of-three 2–0. At 60% per map that happens 36% of the time, so fair odds are about 2.78.