Convert both sides to percentages, add them up, then divide each side by that total. What's left is the book's real opinion with the fee taken out.
The price on your screen is not what the sportsbook thinks is going to happen. It's what they think, plus their cut.
Strip the cut back off and you're left with their actual opinion. That number is the most useful thing on the whole screen, because it's the sharpest estimate available of what's really about to happen, and it's what you should be measuring your own read against.
It takes four steps and about thirty seconds.
How to remove the vig, in four steps
1Convert both sides to a percentage. Say the favorite is -140 and the dog is +120. That's 58.33% and 45.45%.
2Add them together. 58.33 + 45.45 = 103.79%. Anything over 100% is the fee.
3Divide each side by that total. 58.33 ÷ 103.79 = 56.2%, and 45.45 ÷ 103.79 = 43.8%.
4Check your work. Those two now add to 100%. Convert back to odds if you want a price and you get -128 on both sides.
Stripping the juiceRescale both sides so they sum to 100%.
↔ swipe to see the whole diagram
What you actually use it for
Three things, and they all matter.
▸Checking whether you have an edge. If you think a team wins 58% of the time and the fair price says 56.2%, that's a real gap. If the fair price says 61%, you're the one who's wrong.
▸Comparing books properly. Two sportsbooks with different amounts of juice can't be compared at face value. Strip both and you're comparing opinions instead of fees.
▸Grading your closing line value. Comparing your bet to a closing price that still has the fee in it will flatter your numbers. Strip it first.
One thing to know about this method
Dividing everything proportionally like this is the standard first pass, and it's what most calculators do. It isn't perfect. On very lopsided markets it slightly overstates the favorite's real chances, which is why sharper models use weighted versions instead.
For anything priced somewhere near even, the difference is small enough that you can ignore it. If you're grinding heavy favorites at -400 and beyond, it's worth reading up on the weighted methods.
What to do with this
▸Run it on any bet you're about to place, and compare the fair number to your own read.
▸If you can't explain why your number is better than the fair number, you don't have an edge on that bet.
▸Use the no-vig closing price when you grade yourself later, not the raw one.
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