American odds are the format you will see on most US sports sites. They use a plus or minus sign followed by a number, usually at least 100. Once you learn the two rules, you can read any line in a few seconds.
The two rules
Rule 1: Minus numbers show what you risk to win 100. At -150, you risk 150 to win 100. At -110, you risk 110 to win 100. At -300, you risk 300 to win 100.
Rule 2: Plus numbers show what you win on a 100 risk. At +130, a 100 stake wins 130. At +250, a 100 stake wins 250. At +1000, a 100 stake wins 1,000.
The minus side is the favorite, the plus side is the underdog. The bigger the minus number, the heavier the favorite. The bigger the plus number, the longer the shot.
You do not need to bet exactly 100. The 100 is just a reference point, and you scale up or down from there.
Calculating profit for any stake
Here are the formulas:
- Minus odds: profit = stake × (100 ÷ odds)
- Plus odds: profit = stake × (odds ÷ 100)
Your total return is always the stake plus the profit.
Worked example: a favorite at -150
You stake 60 on a team at -150.
- Profit = 60 × (100 ÷ 150) = 60 × 0.667 = 40
- Total return = 60 + 40 = 100
Worked example: an underdog at +130
You stake 60 on a team at +130.
- Profit = 60 × (130 ÷ 100) = 60 × 1.3 = 78
- Total return = 60 + 78 = 138
Notice the asymmetry. The same stake wins less on the favorite because the favorite is more likely to win.
What about -110?
You will see -110 constantly, on point spreads and totals. It means risk 110 to win 100. It is the standard price for a roughly 50/50 market. The 10 extra you risk is essentially the house's fee. If you pick both sides of a -110 market with 110 each, you risk 220 and get back 210 no matter what happens, a guaranteed loss of 10. That is the vig at work.
What about +100 and -100?
Both mean even money. Risk 100, win 100. In decimal terms that is 2.00. It is the price you would get on a perfectly fair coin flip with no house margin.
Converting American odds to implied probability
This is the most useful skill to build, because it tells you what the price assumes.
- Minus odds: odds ÷ (odds + 100)
- Plus odds: 100 ÷ (odds + 100)
Use the number without the sign.
| Odds | Calculation | Implied probability | |---|---|---| | -300 | 300 ÷ 400 | 75.0% | | -150 | 150 ÷ 250 | 60.0% | | -110 | 110 ÷ 210 | 52.4% | | +100 | 100 ÷ 200 | 50.0% | | +130 | 100 ÷ 230 | 43.5% | | +250 | 100 ÷ 350 | 28.6% | | +1000 | 100 ÷ 1100 | 9.1% |
If you think a team's true chance of winning is higher than the implied probability, the price may be good value. If you think it is lower, the price is too short. More on this in our guide to value betting.
Converting American odds to decimal
Decimal odds include your stake, so they are easy to compare.
- Minus odds: 1 + (100 ÷ odds). -150 becomes 1 + 0.667 = 1.67.
- Plus odds: 1 + (odds ÷ 100). +130 becomes 1 + 1.3 = 2.30.
See decimal odds explained for the full picture.
Reading a full game line
A typical NFL listing might look like this:
- Moneyline: Home -165 / Away +140
- Spread: Home -3.5 (-110) / Away +3.5 (-110)
- Total: Over 44.5 (-110) / Under 44.5 (-110)
The moneyline says the home team is favored to win outright, with an implied chance near 62%. The spread says the market expects the home team to win by about three or four points. The total says the market expects around 44 or 45 combined points. Three different questions, three different prices.
Common mistakes with American odds
- Thinking -150 means you lose 150. You only lose your stake if the pick loses. -150 is a ratio, not a fee.
- Comparing minus and plus numbers directly. -120 and +120 are not mirror images in probability. -120 is 54.5%, +120 is 45.5%.
- Ignoring how small favorites add up. Picking lots of -200 favorites feels safe, but you need to win two out of three just to break even. Lose one in three and you are flat.
Practice with play money
Reading American odds becomes second nature with repetition. On MockSport you can make free picks with play-money tokens on real lines and see the exact payout before you confirm. Try converting each line to a probability in your head first, then check yourself. It is a low-pressure way to build the skill. Browse current lines on the odds page.
FAQ
Is -150 or +150 better?
Neither is better in itself. -150 is a favorite with about a 60% implied chance and a smaller payout. +150 is an underdog with about a 40% implied chance and a bigger payout. What matters is whether the price matches the real chance.
Why do both sides of a game sometimes show minus odds?
On point spreads and totals, both sides are designed to be close to 50/50, so both carry a small minus price like -110. The extra above 100 is the house margin.
How much do I win at -110 with a 50 stake?
Profit is 50 × (100 ÷ 110) = about 45.45, so your total return is about 95.45.