Free tool
Odds Converter
Every format of the same price, live as you type. Then the part most converters skip: put in both sides of a market and it shows you the hold — what the book is actually charging — and the fair price underneath it.
Type a price in any of the three boxes. A real American price is −100 or longer, or +100 or longer.
Both sides: hold & fair price
Enter the two sides of a market and it strips the book's margin out — the same de-vig the board runs on every game.
Enter both prices — two sides of the same market.
Hold, and why it isn't the overround
Two prices at −110 each imply 52.38% apiece — 104.76% together. That extra 4.76% is the overround. The hold — the share of money wagered the book expects to keep — is that figure over the total: 4.55%. Books quote the second one, so it's the one shown first.
Removing the margin proportionally gives the fair price. It's the same de-vig the board runs on every game, so a number here and a number in the Fair column always agree.