Alternate Line, in plain words
An alternate line, or alt line, is the same market at a different number than the main line, with a price to match. If a player's main points line is 24.5 at -110, the book may also offer Over 19.5 at -250 or Over 29.5 at +240. The further from the main line, the shorter or longer the price.
Alt lines are where pricing errors hide, because books often build them from a formula rather than from betting interest. Each rung can be checked: turn its price into a chance, and ask whether the player clears that number that often. A ladder priced off a sensible distribution should be smooth; a rung that breaks the pattern deserves a look.
Alt lines are also how bettors build bigger prices in parlays. That is fine when every rung is fair, but a parlay of short alt lines can quietly stack several small margins into one large one.
The idea, drawn
Worked example · illustration
Over 19.5 at −250, main line 24.5 at −110
- Alt line
- Over 19.5
- Price
- −250
- Implied
- 71.43%
- Main line
- 24.5 at −110
- −250 implies 250 / 350 = 71.43%.
- So the bet needs the player to score 20 or more in more than 71.4% of games like this one, margin included.
- If their minutes and role put them at 20 or more less often than that, the alt is overpriced, however safe it feels.
A short alt line is not a safe bet. It is a bet with a high break-even.