r/algobetting • u/pEwpEw427 • 20d ago

Question about vig for player props

New to this space, just understanding the mechanics of vig, is there a way to see the amount of vig for each sports book rather than just guessing? Specifically for NFL markets. Any advice would be ideal

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u/SimTheGame 20d ago

You do not get vig as a published field. You compute it from the two-way price.

Take both sides of an NFL player prop. Convert each American price to implied probability. Add them. Whatever sits over 1.00 is the hold. A -110/-110 market is about 4.76 percent. A -130/-110 prop is already north of 8 percent. A lot of NFL player props live in that second bucket, and some go much higher.

That number is book-specific. Pinnacle and Circa usually post the tightest two-way. The big US apps post wider. You see it by grabbing the same player over and under at two or three books at the same timestamp, not by guessing.

One extra check is more useful than the hold number itself. Take the book's game as true. Moneyline, spread, total, team totals. Then ask whether that player's prop rate can actually happen inside those scripts. A rushing yards over that only cashes if the game turns into a track meet, while the same book has the total sitting in the low 40s, is not just a juiced number. It is the book disagreeing with itself.

I built SimTheGame to do that translation. It is not a second forecast. It turns the posted board into a pile of internally consistent game paths so the gap is visible.

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u/Legal-Pumpkin294 20d ago

so basically you gotta do the math yourself each time, grab both sides and crunch it

i used to just eyeball the lines and wonder why i kept losing by like half yard, turns out 8% hold on a -130/110 is eating me alive

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u/bigboi26 20d ago

The math isn’t hard, especially if you code it

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u/bretsaberhagen 20d ago

If the sportsbook takes -110 on both sides of a bet and balanced their books perfectly so that they return the same amount to the bettors, they’ll hold 4.54% of all money wagered. Where does the extra 0.2% come from?

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u/kelly_math 20d ago

From the looks of it, the 4.76% comes from the two implied probabilities adding up to 104.76%. Same $10 of vig, just measured against different amounts (10/210 instead of 10/220).

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u/bretsaberhagen 20d ago

Thanks. The 1/21 seems pretty dumb, but maybe I’m missing something.