Odds converter and break-even calculator
No-vig fair odds for a two-way line
The converter above takes a price in any of the three formats and rewrites it in the other two, with the implied probability underneath. Type into whichever box matches the number in front of you: -150 in the American box, 2.50 in the decimal box, 10/11 in the fractional box. The other fields update as you type. A plus or minus sign is optional for positive American prices, but a minus price has to carry its minus.
The second row works the other way round and adds your stake. Type a probability, say 55, and the boxes above turn it into the matching price, here about -122. Enter a stake and you see what the ticket wins and what it returns in total. The third row is for your own read of the game: type how often you think the side wins, and the tool shows how far that sits above or below the break-even rate and what the bet is worth on average per $100. A positive number only means your estimate beats the price; it is not a promise that the estimate is right.
The second tool needs two numbers, the prices on both sides of the same line. A moneyline of Team A -140 and Team B +120 is the default. It tells you the margin baked into that pair and what each side would pay if the book took nothing.
Reading a price in three formats
US books quote American odds, so that is where most of you start. Decimal and fractional odds show up in international coverage, older betting guides and some exchange tools, and it helps to read all three without stopping to think.
American odds
A minus number is what you risk to win $100. At -150 you put up $150 to win $100, or $30 to win $20. A plus number is what you win on a $100 stake. At +130, $100 wins $130, and a $25 bet wins $32.50. If you want the basics of how moneylines and run lines are posted before going further, our guide to baseball betting lines covers the board line by line.
Decimal odds
Decimal odds include your stake. Multiply the stake by the price and you get the full return. At 2.50, a $10 bet returns $25: $15 profit plus your $10 back. Converting is quick. A price of 2.50 is +150, because (2.50 - 1) x 100 = 150. Under 2.00 you go the other way: -150 is 1 + 100/150, which is 1.67.
Fractional odds
Fractional odds show profit over stake. 10/11 means you win $10 for every $11 you risk, which is the same bet as -110. As a decimal that is 1 + 10/11, or 1.91. Evens, 1/1, is +100 and 2.00. The converter always writes the simplest fraction that matches the price, so -150 comes out as 2/3 and -110 as 10/11.
Here are the four examples side by side, with the math spelled out:
| Price | American | Decimal | Fractional | Implied probability |
|---|---|---|---|---|
| -150 | -150 | 1.67 | 2/3 | 60.0% |
| +130 | +130 | 2.30 | 13/10 | 43.5% |
| 2.50 | +150 | 2.50 | 3/2 | 40.0% |
| 10/11 | -110 | 1.91 | 10/11 | 52.4% |
Implied probability is the break-even rate
Every price carries a hidden percentage. It is simply 1 divided by the decimal odds. At -150 that is 1 / 1.667, or 60%. At +130 it is 1 / 2.30, or 43.5%.
That number answers the only question that matters before you bet: how often does this have to win for me to come out even? Take -150. You risk $150 to win $100. Win 60 times out of 100 and you collect $6,000, lose 40 times and you give back $6,000. Dead even. So if you think the favorite wins 64% of the time, -150 is a price you like. If you think it is closer to 57%, you are paying too much, even though you expect that team to win.
This is where a lot of baseball bettors trip. They pick winners well and still lose, because MLB favorites are often priced at -180 or -200, which asks for 64% or 67%. A good team at a bad price is a bad bet.
What the no-vig tool does
Books do not deal fair lines. Convert both sides of any market and the two probabilities add up to more than 100%. The extra is the overround, the margin, the vig, the juice. Different names, same thing.
Our default example is -140 against +120. The favorite implies 140 / 240 = 58.3%. The underdog implies 100 / 220 = 45.5%. Together that is 103.8%, so the margin reads 3.8%. On a total or run line dealt at -110 on both sides, each side is 52.4% and the pair adds up to 104.8%, about 4.5% of hold once you express it per dollar wagered.
Removing the margin
To get fair odds, the tool divides each side by the total. 58.3 / 103.8 gives 56.2% for the favorite, and 45.5 / 103.8 gives 43.8% for the dog. Turn those back into prices and you get about -128 and +128. That pair is the market’s opinion with the book’s cut taken out.
Why bother? Two reasons. First, it tells you what a line really thinks. A -140 favorite is not a 58% team in the market’s eyes, it is closer to 56%. Second, it lets you compare apps. If one app deals -140/+120 and another deals -135/+115, the no-vig numbers show you whether they disagree about the game or just charge a different margin.
This method splits the margin in proportion to each side’s probability. It is the standard approach and it works well on moneylines between -200 and +200. On heavy favorites, books tend to pad the underdog side more than the favorite, so the true fair price on a long shot may be a little longer than the tool shows. Keep that in mind on anything past +250.
Using these numbers on a real MLB slate
The math only earns its keep when you have an opinion to test. Start with who is pitching. The probable pitchers board lists every scheduled starter with his numbers, and a late scratch can move a moneyline 30 or 40 cents. If the listed starter changes after you have run the numbers, run them again.
For first-inning bets, the NRFI table gives you how often each team scores or allows a run in the first. Suppose a team’s games stay scoreless in the first inning 58% of the time and the NRFI price is -125. That price needs 55.6%. You have a small edge on paper, before you account for the day’s starters. If the price were -145, which needs 59.2%, you would pass.
Totals work the same way. An under 8.5 at -105 needs 51.2%. The ballpark run environment table shows which parks play high or low, which helps you decide whether 51% is realistic for that game.
For combined bets, the parlay calculator multiplies prices for you and shows how fast the break-even rate falls with each leg. If you want a rough win-by-two probability to hold against a -1.5 price, try the run line simulator.
Small habits that save money
Write the break-even rate next to every bet you consider, not just the price. After a few weeks you start to feel what 57% or 44% means, and you catch yourself before laying -200 on a team you only rate at 62%.
Compare the margin on the same game across two or three legal apps in your state. A line at 3% margin is cheaper to bet than one at 5%, even when the favorite is priced similarly. Over a full 162-game season of betting, that difference is real money.
Set a budget for the season before the first pitch and treat it as money spent on entertainment. Sports betting is for adults 21 and over in states where it is legal, and if it stops being fun, call 1-800-GAMBLER. When you want the bigger picture on how all of this fits together, the home page walks through baseball betting from the first price to the final out.
