How to Calculate Betting Odds
What is Betting Odds?
A betting odds calculator converts between fractional (UK), decimal (European), and American (moneyline) odds formats, and computes implied probability and potential profit.
Formula
Decimal: Profit = (Stake × Odds) − Stake; Fractional a/b: Profit = Stake × a/b; Implied prob = 1 / Decimal odds × 100%
- O
- Odds (decimal) (ratio)
- S
- Stake wagered (currency)
- P
- Probability (%)
Step-by-Step Guide
- 1Decimal odds: profit = (stake × odds) − stake
- 2Fractional a/b: profit = stake × a/b
- 3American +200: profit = stake × 2; −150: stake × 100/150
- 4Implied probability = 1 / decimal odds × 100%
Worked Examples
Input
Decimal odds 3.50, £10 stake
Result
Profit = (10×3.50)−10 = £25; Implied probability = 28.6%
Frequently Asked Questions
What's the difference between decimal and fractional odds?
Decimal (2.50) shows total return per £1. Fractional (3/2) shows profit only. 3/2 decimal = 2.50.
How do American odds work?
+200 means £100 profit on £100 stake; −150 means need £150 stake to win £100.
Can bookmaker odds differ from true probability?
Yes. Bookmakers add margin (overround) so implied probabilities total >100%.