NFL Betting Odds Explained: Fractional, Decimal and American for UK Punters

Three notations, one price, one frustrated UK punter

A reader emailed me a couple of seasons ago with a screenshot showing the same Chiefs moneyline priced at 5/6 on Sky Bet, 1.83 on Matchbook and −120 in a US-based betting podcast notes section. He thought he had spotted an arbitrage. He had not. He had stumbled into the most common confusion in NFL betting for UK punters: three notations of one price, none of them more valid than the others, all of them describing exactly the same wager.

That confusion is more common than it used to be. Super Bowl LVIII pulled in a 91 per cent year-on-year increase in viewers under 35 across the UK. A massive intake of younger fans, many of whom are clicking on an NFL bet slip for the first time, are running into fractional odds without warning. They have read US content, watched US commentary, and now find themselves looking at “5/6” on their account dashboard with no obvious link between what they read and what they see.

This guide is the conversion manual. I will walk through fractional, decimal and American odds one at a time, show you how each one works on a ten-pound stake, then teach you the conversion arithmetic so you never have to wonder again. We will then look at how implied probability lives inside every odds number, what the juice is doing to your expected return, and why the line moves between when it opens and when the ball kicks off.

Fractional odds: the UK default that scares Americans

The first time I tried to explain fractional odds to an American friend, he stared at the screen for a full minute and asked why we did this to ourselves. It looks more complicated than it is. Once you learn to read the slash, the format is more transparent than anything else on the market.

Fractional odds use a numerator-over-denominator format like 5/1 or 7/4. The number on the left is the profit you make. The number on the right is the stake you need to risk to get that profit. So 5/1 means five pounds of profit per one pound staked. 7/4 means seven pounds of profit per four pounds staked. The total return on a winning bet is always profit plus stake — on a 5/1 winner with a ten-pound stake, you make fifty pounds of profit and get your tenner back, for sixty pounds total.

Three categories of fractional odds are worth naming. Anything where the left number is larger than the right — 5/1, 7/4, 11/4 — is “odds against” the bet landing. The bookmaker thinks the outcome is less than 50 per cent likely, and your profit is bigger than your stake. Anything where the left is smaller than the right — 1/2, 4/7, 4/11 — is “odds on” the bet landing. The bookmaker thinks the outcome is more than 50 per cent likely, and your profit is smaller than your stake. And 1/1, which UK sportsbooks call “evens” or sometimes write as “EVS”, is exactly the fifty-fifty case where your profit equals your stake.

A worked example for the most common NFL spread price. Chiefs −7 at 5/6 on a ten-pound stake. You multiply ten by five, divide by six, and you get £8.33 of profit. Total return is £18.33. On a slightly tighter price of 10/11, the calculation is ten times ten, divided by eleven, giving you £9.09 of profit and a total return of £19.09. The penny-level precision tells you the operator is shaving its margin on a competitive market.

One quirk of fractional notation worth knowing. Operators reduce fractions to their lowest terms, but the reduction sometimes makes prices harder to compare. Is 10/11 better or worse than 11/12? They look similar but they are not the same. 11/12 is shorter — pays less profit per pound staked. The fraction “10/11” reduces from “20/22” or “100/110”. When you need to compare two fractional prices quickly, convert both to decimal first. We will come back to that conversion in two sections.

Decimal odds: the European-format that lives on exchanges

Decimal odds are what fractional odds want to be when they grow up and need to do arithmetic in their head. They are the dominant format on betting exchanges, most mobile apps, and basically every European market outside the UK. A decimal price is one number — say 1.83 — and you multiply it by your stake to get your total return.

The mechanic is brutally simple. Ten pounds at 1.83 returns £18.30, of which £8.30 is profit and ten quid is your original stake coming back. Ten pounds at 3.50 returns £35, of which £25 is profit. Ten pounds at 1.10 returns £11, of which one quid is profit on a heavy favourite.

One thing to watch for: decimal odds always include your stake in the return. Fractional odds describe profit only. That is the conversion identity you need to keep straight in your head when comparing the two formats. A fractional 5/1 is a decimal 6.00, not 5.00, because the decimal version includes the stake coming back. A fractional 1/2 is a decimal 1.50, not 0.50.

Why has decimal become the default on so many products? Two reasons. First, the arithmetic is trivial on a phone — multiplication by a decimal number, no fraction reduction, no separate stake addition. Second, comparison across prices is instant. 1.85 is obviously better than 1.83, the way 5/6 versus 10/11 is not obviously anything. For a punter doing line-shopping across two or three sportsbooks before placing a bet, decimal odds save real time.

Most UK sportsbooks let you switch your account display from fractional to decimal in the settings menu. A lot of long-term punters do this and never go back. The fractional notation has cultural value — it is what UK racing has used for two centuries — but for analytical purposes, decimal is the cleaner tool. Use whichever you find easier to read at speed, but be able to convert quickly when you see the other one.

American odds: when a UK punter sees minus signs and gets confused

If you have ever read a US sports-betting article and seen “Chiefs −110” or “Jets +150”, you have met American odds. They are the format used by every US sportsbook and most US analysts, and you will run into them constantly if you follow NFL coverage from American sources. UK sportsbooks rarely display them by default, but a quick reading literacy here saves you time and prevents misunderstandings.

American odds work as two formats stitched together depending on whether the price is favourite or underdog. A minus sign in front means favourite — the number tells you how much you need to stake to win £100. So −110 means you stake £110 to win £100. −150 means you stake £150 to win £100. The bigger the negative number, the heavier the favourite.

A plus sign in front means underdog — the number tells you how much profit you make on a £100 stake. So +150 means you stake £100 to win £150. +300 means you stake £100 to win £300. The bigger the positive number, the bigger the underdog.

The −100 line — sometimes written as “PK” or “pick’em” — is the American equivalent of evens. Stake £100 to win £100, with no implied favourite either way. You will rarely see this on a moneyline because the operator’s margin pushes both sides into negative numbers, but you do see it on point spreads where the line is set to make the game a coin flip.

Where does a UK punter actually need to read American odds? Three places. First, US-based statistical content — sites like Pro Football Focus, US podcasts and Reddit’s sports-betting subreddit all use American odds natively. Second, US-published futures markets, which often leak into UK coverage before UK sportsbooks have set their own lines. Third, the betting podcasts and YouTube channels you might watch for analysis — they will talk about lines as “Chiefs minus three at minus 110” without converting for a UK audience.

The hidden value of being literate in all three formats is that it lets you double-check pricing across markets. If a US analyst is convinced the Bills are a +180 underdog and your UK sportsbook is showing them at 11/4, you can quickly verify whether the UK price is genuinely better, worse, or equivalent. Without the conversion habit, you are guessing.

Converting between the three formats without a calculator

Here is the conversion arithmetic in one place, in the order you will actually need it. None of these require a calculator if you can do basic division in your head — which you can, given a few seconds and a willingness to round.

Fractional to decimal: divide the left number by the right, then add one. 5/1 becomes 5 divided by 1, which is 5, plus 1 equals 6.00. 4/7 becomes 4 divided by 7, which is roughly 0.57, plus 1 equals 1.57. 1/2 becomes 0.5, plus 1 equals 1.50. The “plus one” is for the stake coming back — fractional describes profit only, decimal describes total return.

Decimal to fractional: subtract one, then express what is left as a fraction. 1.83 becomes 0.83, which is roughly 5/6. 2.50 becomes 1.50, which is 3/2 reduced to fractional convention. 3.00 becomes 2.00, which is 2/1. The fraction reduction is where the arithmetic gets fiddly — UK sportsbooks usually choose a standard form like “10/11” or “5/4” rather than the technically reduced version.

Decimal to American: if the decimal is 2.00 or higher, subtract one and multiply by 100. 3.00 becomes 2.00 times 100 equals +200. 2.50 becomes 1.50 times 100 equals +150. If the decimal is below 2.00, take negative 100 and divide by the decimal minus one. 1.50 becomes negative 100 divided by 0.50, which is −200. 1.83 becomes negative 100 divided by 0.83, which is roughly −120.

American to decimal: for positive American, divide by 100 and add one. +150 becomes 150 divided by 100 equals 1.5, plus 1 equals 2.50. For negative American, divide 100 by the absolute value and add one. −200 becomes 100 divided by 200 equals 0.5, plus 1 equals 1.50.

If you do not want to do the arithmetic by hand on every bet, the maths above is exactly what UK conversion calculators handle in one click. My piece on the NFL bet calculator and the tools that handle it walks through which calculators are worth using and which markets they apply to most cleanly. The point of memorising the formulas is not to do the maths every time. It is to sanity-check the calculator output when you are betting with real money.

Implied probability and the juice you pay every time

Every odds number is also a probability number in disguise. The bookmaker has done a calculation: given everything they know, the chance of this outcome happening is roughly X per cent, plus an adjustment for the operator’s margin. The odds you see are the inverse of that probability, with the margin baked in. Reading odds as probability is the first analytical step every serious punter takes.

The conversion is straightforward. Implied probability equals one divided by the decimal odds, expressed as a percentage. A 2.00 decimal price is 1 divided by 2 equals 0.5, or 50 per cent implied. A 1.50 price is 1 divided by 1.50 equals roughly 0.667, or 66.7 per cent implied. A 4.00 price is 1 divided by 4 equals 0.25, or 25 per cent implied.

Now here is where the maths gets interesting. If you add up the implied probabilities on both sides of a fair coin-flip market, you should get exactly 100 per cent. A 2.00 versus 2.00 market — both sides at evens — gives you 50 plus 50 equals 100. That would be a fair market with no margin for the operator.

Look at a typical NFL point spread. Chiefs −7 at −110 American, or 10/11 fractional, or 1.91 decimal. Jets +7 at the same −110 / 10/11 / 1.91. The implied probability on each side is 1 divided by 1.91, which is roughly 52.4 per cent. Add the two sides together and you get 104.8 per cent. The 4.8 per cent over 100 is the operator’s overround — also called juice, vig or margin — and it is the price you are paying for the privilege of betting through them. Point spreads are popular precisely because their pricing is consistent around this margin range, with 61 per cent of NFL bettors using them as their primary market, according to Optimove’s 2025–26 wagering report.

Overround is the central concept of professional betting analysis. A 105 per cent overround on a two-way market means the operator’s edge on the market is roughly 4.8 per cent. A 110 per cent overround means it is closer to 9 per cent. The bigger the overround, the harder it is to make money long-term, because every winning bet has to overcome that gap before it generates any profit.

What does this mean practically? It means a recreational NFL punter is starting roughly 4 to 5 per cent in the hole on every point spread bet, just by paying the operator’s margin. Markets with bigger overrounds — same-game accumulators, exotic prop combinations — start the punter deeper in the hole. Markets with smaller overrounds — major exchanges, the most competitive moneylines — start the punter closer to break-even. That is the entire reason line-shopping across multiple operators matters. You are not just trying to get a better price on this bet. You are trying to compound a smaller overround across a season of bets, where the difference adds up to real money.

Reading a full NFL line from first number to last

Let me pull all this together with a real NFL line you might encounter on a Sunday. The screen shows: Chiefs −7 at 10/11, Jets +7 at 10/11, total 48.5 over at 5/6, total 48.5 under at 5/6, Chiefs moneyline at 1/3, Jets moneyline at 12/5. That is a complete game-day market. Here is what each number means, end to end.

Chiefs −7 at 10/11 — the Chiefs are seven-point favourites, and you can back them to cover that handicap at a price paying you ten pounds of profit per eleven pounds staked. Implied probability is 1 divided by 1.91 equals roughly 52.4 per cent. Jets +7 at 10/11 is the mirror — Jets get a seven-point head start at the same 52.4 per cent implied. Both sides at the same price tells you the operator has set the spread to make the cover a roughly even-money proposition.

Total 48.5 over at 5/6 — the bookmaker projects combined points around 48.5, and the over side at 5/6 pays £8.33 of profit per ten pounds staked. Implied probability is 1 divided by 1.83 equals roughly 54.6 per cent. The under at the same 5/6 carries the same implied 54.6 per cent. Add the two together and you get 109.2 per cent — a meatier overround than the spread, which tells you the operator is taking more margin on totals than on point spreads. This is normal. Totals attract more recreational money and the books price accordingly.

Chiefs moneyline at 1/3 — the Chiefs are heavy favourites to win outright. The 1/3 price pays £3.33 of profit per ten pounds staked. Implied probability is roughly 75 per cent. Jets moneyline at 12/5 — the Jets are big underdogs, with the 12/5 price paying £24 of profit per ten pounds staked. Implied probability is roughly 29.4 per cent. Add 75 plus 29.4 and you get 104.4 per cent — a similar overround to the spread, which makes sense given the two markets describe the same game from a different angle.

What about player props in the same game? Typical QB passing-yards lines on UK bookmakers sit in the 250 to 300 yard range, with passing touchdowns priced at 1.5 to 2.5 and interceptions at 0.5 or 1.5. A Mahomes passing-yards line at 287.5 over at 5/6 implies the book’s projection of his total yards comes out roughly at 287.5 give or take, and that the operator has built in a comparable overround to the totals market. Reading the full set of numbers on a single game-day market is a five-minute exercise once you have done it three or four times. After that, you stop reading numbers and start reading the operator’s view of the game.

Why prices shift before kickoff: sharps, injuries and public bias

The line you saw on Wednesday morning is rarely the line you see on Sunday afternoon. NFL point spreads move continuously between when they open and when the game kicks off, and the reasons they move are surprisingly readable once you know what to look for. Treating line movement as random is a leak. Treating it as signal is an edge.

Sharp money is the first driver. Professional bettors and syndicates place large stakes on early-week openers, often within minutes of the lines being released, because that is when the books are least confident in their numbers. If a Chiefs −6 opener moves to −6.5 by Tuesday evening, that move probably came from sharp action on the favourite. The book has adjusted to protect itself against the people who tend to be right.

Injury news is the second driver and the loudest. A starting quarterback declared out, a left tackle ruled questionable, a primary receiver dealing with a soft tissue issue — any of these can shift a spread by a point or more within minutes. The injury report timing windows are predictable. Wednesday, Thursday and Friday filings during the week, then Saturday and Sunday morning updates closer to kickoff.

Weather is the third driver, mainly on totals rather than spreads. A forecast for sustained 20 mile per hour winds will pull a total down by two to three points by Sunday morning. Cold and snow have less impact than people assume — the impact is mostly already priced. Wind is the underrated weather variable.

Public bias is the fourth driver and the one that creates the most exploitable distortions. Public money tends to back favourites, home teams and high-profile franchises, regardless of the spread. Books know this and will sometimes shade lines against the public — meaning the spread is set slightly worse for the popular side than the model suggests it should be, because the book is sure the public will bet that side anyway.

The UK market has also been growing fast enough that broadcasters comment on NFL traction in their own promotional materials. The Director of NFL at Sky Sports framed the trend at the time of one recent record-setting Super Bowl viewing window: the figures are testament to the continual growth of the NFL in the UK and we’re extremely proud to play a role in helping its expansion into new audiences. Translation for an odds-reader: there is more UK money coming into NFL markets every season, which means more late-week movement driven by recreational bias on the most-televised games. Sky Sports’ three-year deal running through 2027 and roughly 50 per cent more live broadcasts than under the previous contract increases that pull further.

The practical takeaway is that timing your bet matters. If you have a contrarian read against the way the public is moving the line, bet early in the week before the line drifts further away. If your read aligns with where the line is moving, you are already late and the price you wanted is gone.

A quick conversion table you can keep on hand

For when you need to convert in a hurry without doing the arithmetic, here is a reference table running from heavy favourites to long-shot underdogs. The implied probability column is what you actually need to know — it tells you the percentage chance the bookmaker is pricing into the bet.

Fractional	Decimal	American	Implied probability
1/10	1.10	−1000	90.9%
1/5	1.20	−500	83.3%
1/3	1.33	−300	75.0%
1/2	1.50	−200	66.7%
4/7	1.57	−175	63.6%
4/6	1.67	−150	60.0%
5/6	1.83	−120	54.6%
10/11	1.91	−110	52.4%
1/1 (evens)	2.00	+100	50.0%
11/10	2.10	+110	47.6%
6/4	2.50	+150	40.0%
2/1	3.00	+200	33.3%
3/1	4.00	+300	25.0%
5/1	6.00	+500	16.7%
10/1	11.00	+1000	9.1%

One thing the table makes obvious. The implied probabilities for a typical NFL point spread on both sides — 10/11 at 52.4 per cent each — add up to nearly 105 per cent. That five per cent margin is the operator’s edge, and it is broadly consistent across UK NFL markets. Memorising the 10/11 / 1.91 / 52.4 per cent triplet is the single most useful piece of pricing knowledge a beginner UK punter can carry.

Quick answers to common odds questions

A few questions surface again and again when readers move from understanding the formats to using them in practice.

Created by the "NLF Betting Help" editorial team.