Understanding decimal odds
Decimal odds (also called European odds or continental odds) express a bet's price as a single number that represents the total amount returned for each unit staked on a winning bet. The number already includes your stake. If a selection is priced at 2.50, a winning 1-unit bet returns 2.50 units in total: your original 1 unit back plus 1.50 units of profit. This differs from fractional odds (used in the UK and Ireland), where the number shows only the profit relative to the stake — fractional 6/4 is the same price as decimal 2.50.
The three formulas this calculator uses
- Total payout = stake × decimal odds. This is the full amount you receive if the bet wins, stake included. A 100 stake at 2.50 returns 100 × 2.50 = 250.
- Net profit = stake × (decimal odds − 1). Subtracting 1 strips out the returned stake, leaving only your winnings. A 100 stake at 2.50 profits 100 × 1.50 = 150.
- Implied probability = 1 ÷ decimal odds. This is the break-even win chance baked into the price. Odds of 2.50 imply 1 / 2.50 = 0.40 = 40%. Multiply by 100 to read it as a percentage.
Why implied probability matters
The implied probability tells you how often a bet must win just to break even over the long run. If you believe an outcome is more likely than the implied probability, the odds represent positive expected value; if less likely, the price is against you. Note that a bookmaker's implied probabilities across all outcomes of an event sum to more than 100% — the excess is the "overround" or "vig," the built-in margin. For a fair two-way market you would expect the implied probabilities to sum to exactly 100%.
Common reference points
- Evens (2.00): implied probability 50%, profit equal to the stake — double your money.
- Odds-on favourite (below 2.00): e.g. 1.50 implies 66.7% and returns 0.50 profit per unit.
- Underdog (above 2.00): e.g. 5.00 implies 20% and returns 4.00 profit per unit.
- Longshot (10.00): implied probability 10%, profit of 9.00 per unit staked.