How to Read Betting Odds — Decimal, Fractional & American Explained
Published on: July 2, 2026
Why Understanding Odds Matters
If you can't read betting odds, you can't calculate whether a bet is profitable. Every sportsbook, casino, and betting exchange displays odds differently depending on the region. This guide covers all three major formats.
The Three Odds Formats
Decimal Odds (Europe, Australia, Canada)
Decimal odds show your total payout per unit staked, including your original stake.
$$Total\ Payout = Stake \times Decimal\ Odds$$
Example: You bet $100 at 2.50 decimal odds:
- Total payout: $100 × 2.50 = $250
- Profit: $250 - $100 = $150
| Decimal Odds | $100 Bet Payout | Profit | Implied Probability |
|---|---|---|---|
| 1.50 | $150 | $50 | 66.7% |
| 2.00 | $200 | $100 | 50.0% |
| 2.50 | $250 | $150 | 40.0% |
| 3.00 | $300 | $200 | 33.3% |
| 5.00 | $500 | $400 | 20.0% |
Fractional Odds (UK, Ireland)
Fractional odds show your profit relative to your stake.
$$Profit = Stake \times \frac{Numerator}{Denominator}$$
Example: You bet $100 at 3/1 fractional odds:
- Profit: $100 × (3/1) = $300
- Total payout: $100 + $300 = $400
| Fractional | Decimal | American | $100 Profit | Implied Prob |
|---|---|---|---|---|
| 1/4 | 1.25 | -400 | $25 | 80.0% |
| 1/2 | 1.50 | -200 | $50 | 66.7% |
| 1/1 (evens) | 2.00 | +100 | $100 | 50.0% |
| 2/1 | 3.00 | +200 | $200 | 33.3% |
| 5/1 | 6.00 | +500 | $500 | 16.7% |
| 10/1 | 11.00 | +1000 | $1,000 | 9.1% |
American Odds (USA)
American odds use positive and negative numbers.
- Positive (+): How much profit you make on a $100 stake
- Negative (-): How much you need to stake to win $100 profit
$$Profit = \begin{cases} Stake \times \frac{Odds}{100} & \text{if } Odds > 0 \ Stake \times \frac{100}{|Odds|} & \text{if } Odds < 0 \end{cases}$$
Example +200: Bet $100 → win $200 profit (total $300) Example -150: Bet $150 → win $100 profit (total $250)
Quick Conversion Cheat Sheet
| Decimal | Fractional | American | Implied Prob |
|---|---|---|---|
| 1.25 | 1/4 | -400 | 80.0% |
| 1.50 | 1/2 | -200 | 66.7% |
| 1.67 | 2/3 | -150 | 59.9% |
| 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% |
| 5.00 | 4/1 | +400 | 20.0% |
How to Spot Value
Value exists when the true probability of an outcome is higher than the implied probability of the odds.
$$Value = True\ Probability > Implied\ Probability$$
Example: A sportsbook offers 2.50 (40% implied) on a team you believe has a 45% chance of winning.
$$EV = (0.45 \times 1.50) - (0.55 \times 1) = 0.675 - 0.55 = +0.125$$
This is a +12.5% EV bet — profitable in the long run.
Try It Now
Use our Odds Converter to instantly convert between all three formats and see the implied probability.
Use the Is This Bet +EV? tool to check if a bet offers positive expected value.
Related Tools & Resources
- Odds Converter — Convert between decimal, fractional, and American odds
- Is This Bet +EV? — Quick EV checker
- Sports Betting Calculator — Calculate payouts for singles and parlays
- Expected Value Calculator — Full EV analysis
- Kelly Criterion Explained — Optimal bet sizing