What are alternate lines on player props?
Short answer: Alternate lines let you bet a player at a number other than the main line, at a longer or shorter price. Books price them from a projection with a wider margin than the main line, so they usually cost more for the same probability.
What they are
Alternate lines let you bet the same player at a different number than the main line: Over 29.5 points at +180 instead of Over 24.5 at -115, or Over 19.5 at -350. The further from the main line, the longer or shorter the price.
How books price them
Books derive alternate prices from a distribution around their projection. Because these markets are less watched and take less sharp money, books build in a wider margin than on the main line, often noticeably wider at the extremes.
What that means
An alternate line is a different bet, not a better version of the main one. Before taking one, convert its price to a probability (how) and ask whether the player reaches that number that often. Alternate lines are also a common parlay ingredient, where their margins compound (why parlays cost more).
An example of the margin
Suppose the main line is points over 24.5 at -115 and under at -105, a margin of about 4.7 percentage points. The book might offer over 29.5 at +180 and over 19.5 at -350. There is no matching under on those alternates, so you cannot remove the vig the usual way; compare the implied probabilities with how often the player has actually reached those numbers in similar games.
Ladders and same-game parlays
Books market alternate lines as ladders (over 20, 25, 30, 35 points at rising prices) and as pieces of same-game parlays. Both make it easy to stack several long prices, each with its own margin. The arithmetic of stacked margins is the same as in any parlay: they multiply.
When people use them
Bettors use alternates when they think a player's outcome will be far from the main line, for example after a role change the book has not fully priced. The test is the same as for any bet: is the implied probability, after margin, below your honest estimate?
Comparing alternates across books
Not every book offers the same alternate numbers, and prices for the same number can differ more than on main lines, because fewer bettors compare them. If you use alternates, checking two or three books for the same number is worth more here than anywhere else. Market-making books often offer few or no alternates, so there may be no sharp reference price at all.
Related questions
Market data and education only. OpenSlate does not publish free picks and does not tell you what to bet.
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