Decimal odds
Total return is stake multiplied by decimal odds, including the original stake. A $10 stake at 2.50 returns $25 if it wins, for $15 profit.
Implied probability
Divide 1 by decimal odds. Odds of 2.00 imply 50%; odds of 1.50 imply about 66.7%. This is the probability implied by the price, not a forecast.
Understand the margin
For a two-outcome market with both sides priced at 1.91, implied probabilities sum to about 104.7%. The excess over 100% is the overround. It is not a guaranteed realized profit for the bookmaker.
Compare the same market
Check whether prices include overtime, how ties are handled and when an event is settled. Two similar labels may refer to different rules.