Odds converter: American, decimal, fractional and the vig

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Type a price into any of the four boxes (American, decimal, fractional or implied probability) and the other three update to match. The second part takes the odds on both sides of a bet and shows the book’s hold and each side’s fair odds.

Odds converter

Type odds in any box and the other three update.

Bet $100
To win $100

Find the vig on a two-sided line

Enter the American odds on both sides of one bet, such as both teams on the spread or the over and the under.

Implied probability
Break-even win rate
Overround
Book’s hold
Fair probability
Fair odds

American odds are rounded to whole numbers. Fair odds take the book’s cut out of both sides in proportion to their prices, the usual way to estimate them.

How the conversions work

All four boxes describe the same price. Decimal odds are what you get back per $1 bet, stake included. American odds show what $100 wins at a plus price, or what you risk to win $100 at a minus price. Fractional odds show profit over stake, and implied probability is the break-even win rate.

Take -150. You risk $150 to win $100, so each $1 returns 1 + 100 ÷ 150 = 1.667. The profit part, 100/150, reduces to 2/3, and the implied probability is 1 ÷ 1.667 = 60%. At +250, $100 wins $250, which is 3.50 in decimal odds, 5/2 as a fraction and 28.57% implied.

Fractions are reduced to their simplest form. If the exact fraction needs a denominator over 100, the converter shows the closest one that doesn’t and says so, which is why -113 (exactly 100/113) shows as 77/87. Our guide to money lines walks through each formula.

Finding the vig on a two-sided line

A book prices the two sides of a bet so their implied probabilities add up to more than 100%. That total is the overround. The hold is the share of all the money bet that the book keeps, and it’s 1 − 1 ÷ the overround.

Take a money line of -200 and +170. The implied probabilities are 66.67% and 37.04%, an overround of 103.70%, so the hold is 1 − 1 ÷ 1.0370 = 3.57%. If the book took $66.67 on the favorite and $37.04 on the underdog, it would pay out $100 either way and keep $3.70 of the $103.70.

For fair odds, divide each implied probability by the total: 64.29% for the favorite and 35.71% for the underdog, about -180 and +180. Each implied probability is also a break-even win rate, so at -200 you have to win 66.67% of the time, where the fair price asks for 64.29%.

What the vig means for you

You don’t see the hold on any one ticket, but it’s why someone who wins exactly half their bets at -110 slowly loses money. The break-even rate at -110 is 52.38%, and our article on 55 percent winners shows how thin the margin above it is.

It’s also why the price matters. Enter -105 on both sides and the hold drops to 2.38%, about half the 4.55% on a -110 line. On a parlay the cut on every leg stacks up, which the parlay calculator shows for a whole ticket.

Fair odds are an estimate. The converter takes the cut out in proportion to each side’s price, the most common way to do it, though books don’t always spread their margin that way. It also needs exactly two sides, so it won’t handle a three-way bet such as a soccer money line.

Bovada shows odds in American or decimal form, whichever you pick under Profile Settings. It’s an offshore sportsbook with no US state license, and it doesn’t accept players in 19 states and Washington, DC. If your state has legal online sportsbooks, a state-licensed book gives you more protection. Our Bovada review covers the rest.

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