Decimal vs American Odds for MLB: A Converter Walkthrough for UK Punters

Why every US MLB site shows -150 and what it means in 2.50

The first time I tried to copy an MLB pick from an American tout sheet, I lost twenty minutes converting -175 into a stake my UK bookmaker would actually accept. I had a calculator open, a notes app open, and a tab on a US sportsbook screaming about a “lock of the day”. By the time I had translated the number, the line had moved. That afternoon I decided to learn the conversion well enough that I would never sit there staring at a screen again.

Every major MLB analysis site you find through a Google search is American. CBS Sports, Covers, Pickswise, WagerTalk, OddsTrader, Pickdawgz – they all price in the American format. Lines like -150, +130 and -110 are the default vocabulary. If you bet from the UK and want to use that analysis, you need to translate those numbers into the decimal format your bookmaker shows, and you need to do it without thinking. The price -150 becomes 1.67 in decimal. The price +130 becomes 2.30. Once you have done it five hundred times the conversion happens before your brain catches up.

There is a second reason to learn this properly. Even in 2026, UK fan forums and Reddit threads about MLB betting are written in mixed dialect. One poster will quote -135. The reply will quote 1.74. A third will pile in with 3/4 fractional. If you cannot read all three, you are reading half a conversation. Across a 162-game MLB regular season, that is a lot of information you are leaving on the table for no reason other than mental friction.

Decimal odds in 90 seconds

Decimal odds are the cleanest format any betting market has ever produced. The number you see is the total return per pound staked, including your own stake back. A price of 2.50 means a winning £10 bet returns £25 – your tenner plus £15 profit. A price of 1.67 means the same tenner returns £16.70. Multiplication is the only arithmetic involved.

Every UK-facing bookmaker defaults to decimal somewhere in their settings, and Betfair Exchange uses decimal exclusively. The format is also the lingua franca of European books, professional betting communities and almost every modelling tutorial written in the last fifteen years. The reason is simple: decimal lets you compare two prices in one glance. Is 2.10 better than 9/10? You have to convert the second one to find out. Is 2.10 better than 1.95? You can answer in a quarter of a second.

The other quiet advantage is that decimal odds plug straight into implied probability. Divide one by the price and you get the percentage chance the market is giving that outcome. 2.00 becomes 50%. 1.67 becomes about 60%. 4.00 becomes 25%. This is the only mental arithmetic that matters for spotting whether a price represents value, and it works without a calculator.

American odds: the minus and the plus

American odds run on a different logic and they exist for one reason: they predate computerised displays and were designed for a market that quoted prices in units of $100. The format survives because it is what every US sportsbook uses and what every US tipster writes in. Like inches and miles, it is not going away.

The format splits at 100. A minus sign in front of a number means that number is the stake required to win $100. So -150 means you must risk $150 to win $100 in profit. A plus sign means the price pays that many dollars on a $100 stake. So +130 means a $100 stake wins $130 in profit. Even-money is written as -100 or +100 depending on which side of the line the bookmaker chose to round.

The crucial thing for a UK reader is that American odds always come in pairs across a two-sided market. One side carries the minus, the other carries the plus. Pickup an MLB moneyline – say Yankees -135 against the Red Sox +115 – and you immediately know the Yankees are the favourites because their number is negative. The size of the gap between the two numbers tells you the bookmaker’s margin: the bigger that combined imbalance, the more vig the book is taking. A pair like -110/-110 is a tight market with no clear favourite. A pair like -200/+170 has a heavy favourite and a wider spread.

One nuance that confuses everyone at first: minus numbers do not mean the bet pays less than nothing. They mean the implied probability is above 50%. The bet still pays out, just less than your stake in profit terms. A -150 winner returns your $150 plus $100 profit. You are paid; you just had to risk more to claim a hundred.

The two formulas you’ll ever need

Two equations cover every conversion you will ever do. One handles negative American odds. One handles positive. I have these memorised the way a Londoner has the Tube map memorised – not because I am proud of it, but because the alternative is fumbling at one in the morning when MLB lines are moving.

For negative American odds, divide 100 by the absolute value of the American price, then add 1. So -150 becomes 100 ÷ 150 + 1 = 0.667 + 1 = 1.67 decimal. -110 becomes 100 ÷ 110 + 1 = 0.909 + 1 = 1.91 decimal. -200 becomes 0.5 + 1 = 1.50 decimal. The smaller the original number, the bigger the underlying favourite, the smaller the decimal price.

For positive American odds, divide the American price by 100, then add 1. So +130 becomes 130 ÷ 100 + 1 = 1.30 + 1 = 2.30 decimal. +200 becomes 2 + 1 = 3.00 decimal. +450 becomes 4.5 + 1 = 5.50 decimal. The bigger the positive number, the bigger the underdog, the bigger the decimal price.

Going the other way is just as quick. If decimal is above 2.00, subtract 1 and multiply by 100 to get the positive American odds. So 2.30 – 1 = 1.30; 1.30 × 100 = +130. If decimal is below 2.00, divide -100 by (decimal – 1) and you get the negative American odds. So 1.67: 1.67 – 1 = 0.67; -100 ÷ 0.67 = -149 (rounded to -150 by bookmakers). Decimal 2.00 sits exactly at the dividing line and converts to +100 or -100 depending on convention.

Three worked MLB conversions

Let me run through three real-world examples drawn from typical MLB pricing. Around 28% of MLB games each season finish with a one-run margin, which is part of why moneyline prices on tight matchups cluster heavily around the -110 to -130 range. So the examples I am picking are not edge cases – they are the daily wallpaper of an MLB card.

First, a tight divisional matchup. American odds: Phillies -120 / Mets +100. Converting the Phillies side: 100 ÷ 120 + 1 = 1.83 decimal. Converting the Mets side: 100 ÷ 100 + 1 = 2.00 decimal. So your decimal-bookmaker would show 1.83 and 2.00 on the same matchup. A £100 stake on the Phillies returns £183 (£83 profit). A £100 stake on the Mets returns £200 (£100 profit).

Second, a clear favourite with a top pitcher on the mound. American odds: Dodgers -180 / Pirates +160. Converting: 100 ÷ 180 + 1 = 1.56 for the Dodgers; 160 ÷ 100 + 1 = 2.60 for the Pirates. The gap between 1.56 and 2.60 – and the implied probabilities of about 64% and 38% adding to roughly 102% – tells you the book is taking about 2% vig on this matchup.

Third, a heavy favourite, where most UK punters meet their first ugly surprise. American odds: Braves -250 / Marlins +210. The Braves come out at 100 ÷ 250 + 1 = 1.40 decimal. The Marlins come out at 210 ÷ 100 + 1 = 3.10 decimal. A £100 stake on the favourite returns just £140. This is where the run line at ±1.5 starts to look attractive – and where, for context, the ±1.5 spread becomes a different conversation entirely. The decimal price for a -1.5 run line on a heavy favourite typically sits somewhere between 2.00 and 2.40, depending on the pitcher.

And what about fractional?

UK horse racing still runs on fractional odds and a stubborn slice of UK punters set their bookmaker accounts to fractional by default. So you will see MLB lines like 4/5, 11/10 and 6/4 in domestic sportsbooks. Fractional is the most cumbersome of the three formats for baseball because the numerators and denominators get awkward fast, but here is how it works.

A fractional price tells you the profit per unit of stake, not the total return. So 4/5 means a £5 stake returns £4 profit (£9 total). 11/10 means a £10 stake returns £11 profit (£21 total). 6/4 means a £4 stake returns £6 profit (£10 total). Anything below evens (1/1) means a favourite; anything above means an underdog. Evens – written as 1/1 – equals 2.00 decimal and +100 American.

To convert fractional to decimal, divide the first number by the second and add 1. So 4/5 becomes 0.8 + 1 = 1.80. 11/10 becomes 1.10 + 1 = 2.10. 6/4 becomes 1.5 + 1 = 2.50. Going the other way: take decimal, subtract 1, then express the result as a fraction. 1.67 minus 1 is 0.67, which the bookmaker writes as 4/6 or simplifies to 2/3.

My recommendation: pick decimal and never look back. Set every bookmaker account you have to decimal display in the settings. Convert other formats as needed, but do your own thinking in decimal. The maths of expected value, the maths of margin, the maths of implied probability – all of it is cleaner in one format. Mixing formats is a self-inflicted wound.

One last note on rounding and the small print

Bookmakers round their displayed odds. American sportsbooks round to the nearest five (or sometimes ten) on the minus side, so a true price of -148 becomes displayed -150. UK decimal bookmakers tend to round to two decimal places, so a true 1.673 becomes 1.67. Betfair Exchange shows three decimal places on big markets and two elsewhere. These rounding conventions cost you a tiny edge – usually a percent or two on the margin – but they are universal and you cannot avoid them.

What you can avoid is converting incorrectly under time pressure. Write the two formulas out on a sticky note, stick it to your monitor for two weeks, and by the third week you will not need the note. From there, the next step is doing something useful with the converted number – and that means turning it into implied probability and expected value, which is the only reason any of this matters.