American Odds to Decimal Conversion — Formulas, Tables and Quick Methods
Available in US
The first time I saw -150 next to a team name, I genuinely did not know whether that was a good price or a bad one. I had been betting football in decimal odds for years — 1.67 made instant sense to me, but -150 was a foreign language. It took me one evening with a calculator and a notepad to crack the formulas, and I have never looked back. Once you understand how American odds translate to decimal, you stop being confused by MLB lines and start evaluating them on equal footing with any other market.
Sports betting accounts for 56.64% of all online gambling revenue in the UK, and the overwhelming majority of that action uses decimal or fractional odds. But MLB lines originate in the United States, where American odds are the standard. Andrew Rhodes, CEO of the UK Gambling Commission, made an interesting observation at ICE 2025 when he noted that consumer staking does not necessarily track with inflation — bettors tend to stake in round figures regardless of the pricing format. For UK bettors moving into MLB, the format barrier is psychological, not mathematical. These two formulas dissolve it completely.
Converting Positive American Odds
Positive American odds indicate the underdog — the team expected to lose — and the number tells you how much profit you would make on a 100-unit stake. A line of +150 means a 100-unit bet returns 150 units of profit plus your original stake. Converting that to decimal is a single step.
The formula: Decimal = (American odds / 100) + 1.
Take +150. Divide by 100, and you get 1.50. Add 1, and the decimal equivalent is 2.50. A ten-pound bet at 2.50 returns twenty-five pounds total — fifteen profit plus the ten-pound stake. The maths holds for any positive number. +130 becomes (130 / 100) + 1 = 2.30. +200 becomes (200 / 100) + 1 = 3.00. +110 becomes (110 / 100) + 1 = 2.10.
The mental shortcut I use: move the decimal point two places left, then add one. +140 becomes 1.40, then 2.40. It takes a second, and after a few weeks of practice, you stop needing to think about it consciously. The number just registers in both formats simultaneously.
Where this matters practically is in evaluating underdog value. A +155 MLB underdog converts to 2.55 in decimal, implying a win probability of about 39.2%. If your analysis gives that team a 42% chance, you have a value bet — and you spotted it because you could instantly read the decimal equivalent rather than staring at a plus sign and guessing.
Converting Negative American Odds
Negative odds indicate the favourite, and the number tells you how much you need to stake to make 100 units of profit. A -150 line means you stake 150 units to profit 100. The conversion formula is slightly different from the positive side.
The formula: Decimal = (100 / absolute value of American odds) + 1.
Take -150. Divide 100 by 150, and you get 0.667. Add 1, and the decimal equivalent is 1.667 — which any UK bettor would recognise as a moderate favourite, roughly comparable to a top-six Premier League side hosting a mid-table opponent. The UK ranks third globally in gambling market size at 27 billion dollars, and the vast majority of bettors in that market think in decimal. Converting MLB favourites into that format puts them on familiar ground. For a deeper look at how these formats interact with margin and implied probability, our MLB betting odds guide covers the full framework.
More examples: -130 becomes (100 / 130) + 1 = 1.769. -200 becomes (100 / 200) + 1 = 1.500. -110 becomes (100 / 110) + 1 = 1.909. Each of those decimal numbers will feel instantly familiar if you have spent any time betting on football or rugby — and that familiarity is the whole point. You are not learning a new skill. You are translating a known skill into a different context.
The mental shortcut for negatives is less elegant than for positives, but it works: ask yourself “how many times does the number go into 100?” For -200, the answer is 0.5, plus 1 gives 1.50. For -125, the answer is 0.8, plus 1 gives 1.80. Close enough for a quick assessment; use the precise formula when you need to compare lines across sportsbooks.
Conversion Reference Table
I keep a printed reference table next to my laptop, and even after years of converting on the fly, I still glance at it when I want to be precise. Here are the most common MLB lines you will encounter, with their decimal and implied probability equivalents.
+200 = 3.00 (implied 33.3%). +175 = 2.75 (36.4%). +150 = 2.50 (40.0%). +140 = 2.40 (41.7%). +130 = 2.30 (43.5%). +120 = 2.20 (45.5%). +110 = 2.10 (47.6%). -110 = 1.909 (52.4%). -120 = 1.833 (54.5%). -130 = 1.769 (56.5%). -140 = 1.714 (58.3%). -150 = 1.667 (60.0%). -160 = 1.625 (61.5%). -175 = 1.571 (63.6%). -200 = 1.500 (66.7%).
Notice the asymmetry. Moving from -110 to -200 on the favourite side corresponds to a decimal range of 1.909 to 1.500 — a span of 0.409. Moving from +110 to +200 on the underdog side corresponds to 2.10 to 3.00 — a span of 0.90. The underdog side stretches further in decimal terms, which is why underdog value is easier to spot in decimal format. A small movement in American odds (+140 to +155, say) translates to a noticeable shift in decimal (2.40 to 2.55), making it clearer that the price has changed meaningfully.
I recommend bookmarking or printing this table until the conversions become automatic. Most UK sportsbooks allow you to toggle between odds formats in settings, but some default to American for MLB, and having the mental framework to read both saves time when lines are moving quickly before first pitch.
What is the exact formula for converting positive and negative American odds to decimal?
For positive American odds: Decimal = (American odds / 100) + 1. For negative American odds: Decimal = (100 / absolute value of American odds) + 1. These formulas are mathematically precise and produce the exact decimal equivalent for any American odds line.
Do I lose accuracy when converting American odds to decimal for calculation purposes?
No. The conversion formulas produce mathematically exact equivalents. A -150 American line is precisely 1.6667 in decimal, and calculating your payout with either format yields an identical result. The only source of apparent discrepancy is rounding — if a sportsbook displays 1.67 instead of 1.6667, the difference is cosmetic and affects the display, not the actual payout calculation.
Created by the ”Online Baseball Betting” editorial team.
