Totals (over/under)
A bet on whether the combined goals, points or games in an event land above or below a line the bookmaker sets.
A totals market splits outcomes at a number. Over 2.5 goals wins with three or more; under 2.5 wins with two or fewer. The same idea applies to points in basketball, games or sets in tennis, and maps or rounds in esports. In soccer, totals are settled on regular time only, including stoppage time; extra time and penalties do not count unless the market says so.
The maths
Illustrative soccer prices: Over 2.5 at 1.85, Under 2.5 at 2.00.
- Implied: 1/1.85 = 54.05%; 1/2.00 = 50.00%; total 104.05%.
- Book margin (overround): 4.05%.
- Fair probabilities: 51.9% over, 48.1% under; fair odds about 1.92 and 2.08.
A $40 stake on the over returns $74 if the match ends 2-1.
Modelling a total
A common starting point is the Poisson distribution. If a match is expected to produce 2.7 goals in total, the probability of two or fewer is e^(-2.7) × (1 + 2.7 + 2.7²/2) = 49.4%, so over 2.5 is about 50.6%. Real models adjust for score effects and team styles, but this shows how a line is built.
Quarter lines
Lines such as 2.25 or 2.75 split your stake across two neighbouring lines, as in Asian handicap. Compare the margin on these with the main line using overround.