Available in USContent
The Conversion You Should Be Able to Do in Your Head
The first NFL preview I ever read came from an American website that priced everything in plus and minus signs and assumed you spoke fluent gibberish. I spent twenty minutes with a calculator translating odds into fractions before I realised the game I wanted to bet had already kicked off. As Henry Hodgson, NFL UK’s General Manager, has said in conversation with Sky Sports, the London games are a continued catalyst for year-round fan engagement, with over 15 million UK fans now in the league’s orbit – and the practical consequence of that growth is that British punters are reading American previews, American odds, American maths, every single week.
You do not need to master American odds. You need to convert them in your head in under three seconds. This piece is the conversion logic and the cheat sheet I taped to my desk during my first NFL season.
Positive American Odds: The Easy Direction
A positive American number tells you what £100 returns in profit. Plus 250 means a £100 stake wins £250 in profit. That is straightforward. The fractional equivalent is the American number over 100, simplified. Plus 250 becomes 250/100, which simplifies to 5/2. Plus 150 becomes 150/100 or 3/2. Plus 400 becomes 4/1.
The mental shortcut is simple: drop the plus sign, divide by 100, that is your fractional. If the result is messy – plus 230 gives 230/100 – you can usually leave it as 23/10 or convert to decimal (3.30) and work from there. Most UK punters who deal in American odds settle on decimal as the common middle ground because it is the format that does not need conversion in either direction.
A useful sanity check on a positive American line: anything plus 100 or higher is, in fractional terms, evens or better. The dog is paying more than even money. The further the plus number is from zero, the longer the dog.
Negative American Odds: The Direction That Trips Punters Up
A negative American number tells you what you must stake to win £100 profit. Minus 200 means you stake £200 to win £100. Minus 150 means you stake £150 to win £100. The fractional equivalent is 100 over the absolute value of the American number, simplified. Minus 200 becomes 100/200 or 1/2. Minus 150 becomes 100/150 or 2/3. Minus 300 becomes 100/300 or 1/3.
This is where conversions go wrong. Punters used to fractional odds read minus 200 and try to remember whether that is the same as evens or the same as 1/2. The answer is always shorter than evens – a minus sign in American means a favourite, and favourites in fractional always read as numerator smaller than denominator. If you remember nothing else, remember that any minus number is shorter than evens.
The shortcut here is harder than the positive direction. Minus 200 is 1/2. Minus 300 is 1/3. Minus 400 is 1/4. Beyond those round numbers, the conversion gets messy. Minus 110 – the standard NFL spread price – is the one to memorise: it equals 10/11 in fractional. Every NFL spread you ever bet will be at minus 110 unless the book has shifted the line a half-point.
The Cheat Sheet You Should Memorise
These are the conversions that cover roughly 95% of NFL pricing. Memorise these and you can read any American board fluently without thinking.
Minus 110 equals 10/11, decimal 1.91, implied probability 52.4%. This is the standard NFL spread price on both sides. Minus 120 equals 5/6, decimal 1.83. Minus 130 equals 10/13, decimal 1.77. Minus 150 equals 2/3, decimal 1.67. Minus 200 equals 1/2, decimal 1.50. Minus 250 equals 2/5, decimal 1.40. Minus 300 equals 1/3, decimal 1.33. Minus 400 equals 1/4, decimal 1.25. Minus 500 equals 1/5, decimal 1.20.
On the plus side, plus 100 is evens or 1/1, decimal 2.00. Plus 110 is 11/10, decimal 2.10. Plus 130 is 13/10, decimal 2.30. Plus 150 is 3/2, decimal 2.50. Plus 200 is 2/1, decimal 3.00. Plus 250 is 5/2, decimal 3.50. Plus 300 is 3/1, decimal 4.00. Plus 400 is 4/1, decimal 5.00. Plus 500 is 5/1, decimal 6.00.
That covers most of the prices you will see on a Sunday slate. The UK had 5,825 betting shops and 8,234 licensed gambling premises in 2024-25, and across that retail and online estate, NFL prices appear in fractional form even when the underlying lines were built in American. Knowing the conversions both directions saves you from reading the wrong number on the wrong screen.
The Decimal Bridge
If you do not want to memorise the table above, learn decimal odds and convert in one direction only. Decimal odds are intuitive: 2.50 means a £1 stake returns £2.50 including stake. The conversion to fractional is mechanical – subtract 1 from the decimal and that gives you the fractional value. Decimal 2.50 becomes 1.50, which is 3/2.
From American to decimal: positive American divided by 100 plus 1 gives you the decimal. Plus 250 becomes 2.5 plus 1, or 3.50. Negative American is harder – 100 divided by the absolute value plus 1. Minus 200 becomes 0.5 plus 1, or 1.50.
I have settled on decimal as my working format because it scales gracefully across accumulators (multiply the decimals to get the combined price) and because it represents stake-plus-return rather than just return. The fractional format is what UK books display by default; the American format is what every US-based preview uses; the decimal format is the bridge that lets you move between the two without thinking.
The Mental Maths That Saves You Time
Four shortcuts I use every Sunday. First, minus 110 equals 10/11 – say it ten times before your first NFL Sunday, it is the most-quoted price in American sports. Second, anything plus 100 or higher pays more than even money; anything minus 100 or worse pays less. The line at exactly plus 100 or minus 100 is a coin flip in price terms. Third, halve and add – plus 200 means double your stake, minus 200 means halve your return. Quick directional checks rarely fail you.
Fourth, work in implied probabilities rather than odds for any complex comparison. Plus 150 is 40% implied. Minus 150 is 60% implied. If a leg you are considering has roughly a 50% chance of winning in your model, anything priced shorter than evens means you are taking the worse end of the trade and anything longer than evens means the book has given you a small edge. Implied probability is the universal language. Once you can convert American or fractional into implied probability in your head, the price format does not matter any more.
The implied probability layer is where the conversions become genuinely useful – translating any price into a true win-rate estimate is the foundation of every value bet I make, and the no-vig methods I use to strip the margin from any NFL line walk through the exact maths step by step.
What is minus 110 in UK fractional odds?
10/11. This is the single most quoted American odds price in NFL betting – the standard spread price on both sides of nearly every game – and it is the conversion every UK punter who reads American previews should commit to memory. Decimal equivalent is 1.91, implied probability 52.4%.
How do I convert plus 250 instantly?
Drop the plus sign, divide by 100. Plus 250 becomes 250/100, which simplifies to 5/2. That is fractional. For decimal, just divide by 100 and add 1 – plus 250 equals 3.50 decimal. Both directions take roughly two seconds once you have done them a handful of times.
