How to Read Betting Odds
Odds tell you two things: the payout and the implied probability. This guide explains decimal, fractional and American formats, how to convert odds to a percentage, and the bookmaker margin that quietly shapes every price. Code VIP4YOU unlocks a 130% / $130 bonus.
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Every price you see is a number doing two jobs at once: it tells you how much a winning bet pays, and it encodes the chance the bookmaker gives that outcome. Learn to read both and you stop betting blind. This is the one foundation that makes every other market — handicaps, totals, accumulators — make sense.
The three odds formats
- Decimal (1.50, 2.50, 4.00) — total return per unit, stake included. The default on 1xBet and the easiest to calculate with.
- Fractional (1/2, 3/2, 3/1) — profit relative to stake; traditional in the UK. 3/1 means $3 profit per $1 staked.
- American (−200, +150, +300) — minus is the favourite (stake to win $100), plus is the underdog (profit on a $100 stake).
Conversion & implied probability table
| Decimal | Fractional | American | Implied probability |
|---|---|---|---|
| 1.25 | 1/4 | −400 | 80.0% |
| 1.50 | 1/2 | −200 | 66.7% |
| 1.91 | 10/11 | −110 | 52.4% |
| 2.00 | 1/1 | +100 | 50.0% |
| 2.50 | 3/2 | +150 | 40.0% |
| 3.00 | 2/1 | +200 | 33.3% |
| 4.00 | 3/1 | +300 | 25.0% |
| 6.00 | 5/1 | +500 | 16.7% |
Switch formats instantly with the odds converter tool.
Implied probability — the number that matters
The formula
Implied probability = 1 ÷ decimal odds. Odds of 2.50 → 1 ÷ 2.50 = 0.40 = 40%. That's the chance the bookmaker is pricing. If you think the real chance is higher than 40%, the bet has positive expected value; if lower, it doesn't. Every bet is a comparison of your estimate vs the implied probability.
The bookmaker margin (overround) — the hidden edge
Add up the implied probabilities of all outcomes in a market and you'll get more than 100%. That surplus is the margin:
- Fair coin (no margin): each side 2.00 (50% + 50% = 100%).
- With margin: a book might offer 1.91 / 1.91 (52.4% + 52.4% = 104.8%) — a 4.8% overround.
- Why it matters: a lower-margin book pays more on the same outcome. Over hundreds of bets, margin is the difference between break-even and slow bleed.
Favourites, underdogs and "value"
- Favourite — low odds, high implied probability (e.g. 1.40 = 71%). Wins often, pays little.
- Underdog — high odds, low implied probability (e.g. 4.00 = 25%). Wins rarely, pays big.
- Value — not "will it win?" but "are the odds bigger than the true chance?" Backing a 25% shot at 5.00 (implied 20%) is value even though it usually loses.
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Reading odds — FAQ
Are decimal and fractional odds different prices?
No — they're the same price in different notation. 2.00 decimal = 1/1 fractional = +100 American.
Why do all the probabilities add up to over 100%?
That's the bookmaker margin (overround) — the built-in edge. Lower-margin books offer better value.
How do I actually place a bet once I understand odds?
See how to bet on football for the full step-by-step from registration to withdrawal.
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