A book posts -110 on both sides of a coin-flip game. Add up the implied probability behind each price and the total comes to 104.76%, not 100%. That extra 4.76% is the hold, the book’s built-in cut, and it’s baked into the price before a bettor ever sees it.
The no-vig fair odds calculator strips that cut out and shows what each side would pay in a market with no hold at all. That fair number is what a bettor’s own probability estimate should be measured against, not the raw price on the board, since the raw price always makes every side look a little worse than its true chance.
Enter the odds for Side 1 first, typed in American format such as -110 or +150. Enter Side 2 odds the same way. If the market has three possible outcomes, such as a soccer match with a draw, enter Side 3 odds; leave that field blank for a straight two-way market like a moneyline or a spread.
Once the odds are entered, the result shows fair odds for each side, given as both an American price and a percentage. Below that sits the book’s hold, the extra probability priced into the market, and the total implied probability all sides add up to before that hold gets removed.
A price of -110 implies roughly a 52.38% chance of winning. Two sides both priced at -110 add up to 104.76% total implied probability, not the 100% a true coin flip would carry. That extra 4.76% is the hold: money the book keeps regardless of who wins.
To get the fair price, each side’s implied probability gets divided by that total. At -110 and -110, each side’s 52.38% divided by 104.76% comes out to exactly 50.0%, which converts back to +100. That’s the fair price of a true coin flip with the margin removed, and it’s what the calculator returns for the default example: +100 (50.0%) on each side, a 4.76% hold, and 104.76% total implied.
The fair odds matter most when a bettor already has an independent probability estimate for a side. If that estimate is higher than the fair probability shown here, the price offers value. If it’s lower, the payout only looks good because the posted number still carries the book’s cut.
A common mistake is comparing a projection straight against the posted odds instead of the fair odds. Posted odds still include the hold, so every side looks worse than its actual chance. Removing the vig first gives a clean number to test a projection against.
Hold size varies by book and by market. A sharp bettor checks it across shops, since a smaller hold means less ground to make up before a bet can turn a profit.
What counts as a good hold on a two-way line? Smaller is better. The -110/-110 example carries a 4.76% hold, and any market priced meaningfully higher than that is taking a bigger cut out of both sides.
Why don’t fair odds match either side’s posted price? Because the posted price includes the hold. Fair odds show what’s left once that extra probability is stripped out and each side’s chance is scaled back to add up to exactly 100%.
Does adding a draw change how the math works? No. With three outcomes, each side’s implied probability still gets added up and divided by the total; the calculator just runs three numbers through the same method instead of two.
Can a bettor actually place a bet at the fair odds? No book offers them. Fair odds exist as a benchmark, a number to compare a personal probability estimate or a shopped price against, not a line that shows up on a board.