Two screens, two prices, one match: a bookmaker quoting 6/4 in one place and 2.50 in another is offering the same return, yet plenty of readers treat them as different deals. That confusion costs money at the point of placing a bet, and it is the first thing to fix before you start hunting the BestOdds UK markets or comparing welcome offer terms. Fractional odds, the 6/4 and 11/10 format used across UK high street and online books, express profit relative to stake. Decimal odds, the 2.50 and 3.60 format common on exchange-style interfaces, express total return including the stake. One number is net, the other gross.
The thesis of this primer is simple: once you can convert between the two formats in your head, prices become comparable, and comparison is where value lives. A £10 free bet or 250 free spins is only worth what the underlying odds allow you to extract, and bonus terms at any UK online casino or sportsbook are written in the same numbers you need to read at the point of staking. Get the arithmetic wrong and a generous-looking promotion can quietly turn into a losing proposition.
The worked examples that follow stay deliberately small: evens, 5/2, 11/10, 2.50, 3.60. Each conversion is a single step, addition or subtraction of one, and each one you practise makes the next comparison faster. By the end you should be able to look at a fractional board and a decimal board side by side and know, without a calculator, which side is paying more.
What fractional and decimal odds actually represent
Fractional odds: profit measured against stake
Fractional odds are the traditional British format and they answer one question: how much profit do I make for each unit staked? The number on the left is the profit, the number on the right is the stake. So 6/4 means £6 of profit for every £4 staked. Put £4 on a 6/4 shot and a winning bet returns £10 in total: your £4 back plus £6 profit.
The same logic holds across the board. Evens (1/1) doubles your money in profit terms, 5/2 pays £5 profit per £2 staked, and 11/10 pays £11 per £10. Short prices such as 1/4 tell you the outcome is heavily fancied: £1 profit for every £4 risked. Fractional odds never include the return of your stake in the price, which is why the profit figure and the total return are two different numbers.
Decimal odds: total return in a single number
Decimal odds, standard across most of Europe and Australia and increasingly common at UK online casino and sportsbook brands, express the total amount that comes back to you, stake included. A price of 2.50 means every £1 staked returns £2.50 on a winner: £1.50 profit plus your £1 stake. Multiply the stake by the decimal price and you have the full return without any further arithmetic.
That single-number design makes decimal odds quick to compare and quick to settle. Three outcomes priced at 2.50, 3.40 and 4.20 can be ranked at a glance, and a £25 bet at 3.40 returns £85 with one multiplication. The trade-off is that the stake is buried inside the price, so the profit is not visible until you subtract 1.
The two formats describe the same probability and the same payout, just from different starting points. Fractional odds isolate profit; decimal odds bundle profit and stake together. That difference is the whole basis of the conversion: decimal equals fractional plus one. Once a beginner sees 6/4 and 2.50 as the identical price rather than two competing offers, reading odds across UK bookmakers stops being a source of confusion and starts being a source of edge.
Why decimal odds include your stake and fractional odds do not
The difference comes down to what each format is measuring. Fractional odds describe profit only. Decimal odds describe the total you get back, stake included. A price of 6/4 says: for every £4 you stake, you make £6 profit, and your £4 comes back on top, so £10 lands in your account. The same bet at 2.50 decimal returns the same £10, but the number itself already contains the stake. That is the whole distinction in one line: 2.50 decimal equals 6/4 fractional, and the quick conversion is decimal = fractional + 1.
Run the arithmetic and it holds across the board. Evens, written 1/1, becomes 2.00 decimal. 5/2 becomes 3.50. 11/10 becomes 2.10. In every case you divide the top number by the bottom number, add one, and you have the decimal price. Going the other way, subtract one from the decimal and turn what is left back into a fraction: 3.50 minus 1 is 2.50, which is 5/2. The “+1” is not a quirk of notation. It is the returned stake being folded into the price.
This is where beginners trip up. A new customer sees 6/4 at one bookmaker and 2.50 at another and assumes the second is the better price, because 2.50 looks bigger than 1.5. It is not. They are the same bet paying the same money. The error is comparing a profit figure with a total-return figure, which is like comparing a wage with a wage plus a refunded deposit. Once you convert both to one format, the comparison is honest and the choice becomes obvious.
The practical consequence is that decimal odds flatter short prices. A 1.20 decimal price looks substantial next to 1/5 fractional, yet they are identical, and both return just £1.20 on a £1 stake. Fractional odds make the same point more bluntly: you are risking £5 to win £1. Neither format is more generous. They are two labels on one price.
For anyone claiming a welcome offer, the distinction matters before you stake a penny. A £10 free bet at 6/4 returns £15 profit, because the stake is not yours to lose. The same £10 at 2.50 decimal, read as if the stake were included in your return, would suggest £25. It is not. Read the terms, convert the odds, and the real value of any betting promotion becomes clear.
Converting between fractional and decimal odds step by step
The arithmetic runs in two directions and neither is difficult once the rule is fixed in your head. To go from fractional to decimal, divide the top number by the bottom number and add 1. The division gives you the profit per unit staked; the plus one returns your stake to the price. Take 6/4: six divided by four is 1.5, and 1.5 plus 1 equals 2.50. A £10 stake at 6/4 returns £25 in total, of which £15 is profit.
Going the other way, subtract 1 from the decimal price and convert what remains back to a fraction. Take 2.50: minus 1 leaves 1.50, which is the same as 3/2. Note that 3/2 and 6/4 are the same price written differently, and bookmakers use both. To reduce a fraction, divide top and bottom by their highest common factor: 6 and 4 both divide by 2, giving 3/2, and as explained at https://bestodds-online.uk/ the decimal conversion is unaffected by which version you read.
Run the same steps across the fractions you will meet most often:
| Fractional | Working | Decimal | Return on £10 |
|---|---|---|---|
| Evens (1/1) | 1 / 1 + 1 | 2.00 | £20 |
| 11/10 | 11 / 10 + 1 | 2.10 | £21 |
| 6/4 | 6 / 4 + 1 | 2.50 | £25 |
| 5/2 | 5 / 2 + 1 | 3.50 | £35 |
| 1/2 | 1 / 2 + 1 | 1.50 | £15 |
Evens is the cleanest check on the method. A 1/1 price means £1 profit per £1 staked, so the decimal equivalent must be 2.00, and it is. Anything shorter than evens produces a decimal below 2.00: 1/2 becomes 1.50, 2/5 becomes 1.40, 1/3 becomes 1.33 recurring. Anything longer sits above 2.00: 5/2 becomes 3.50, 4/1 becomes 5.00, 10/1 becomes 11.00. If a conversion lands on the wrong side of 2.00, you have added the stake twice or not at all.
Recurring decimals are the one place the arithmetic gets untidy. A 1/3 price is 1.333…, usually shown as 1.33, and a 2/7 price is 1.2857…, rounded to 1.29. Bookmakers round to two decimal places, so a converted price can differ by a hundredth from the exact figure. When you are comparing two prices that sit within 0.01 of each other, treat them as level and check the place terms instead of chasing the rounding.
Spotting value when bookmakers price in different formats
UK bookmakers are free to display odds in whichever format they choose, and many switch between fractional and decimal depending on the sport, the market or the device. The result is that the same price can appear in two different guises on the same afternoon. A football price shown as 6/4 at one sportsbook and 2.50 at another is not a difference of opinion; it is the same number wearing different clothes. Until you convert both to a common format, you cannot tell a genuine value gap from a formatting quirk.
The procedure is straightforward. Convert every price to decimal, because decimal odds make the total return per £1 staked immediately visible. Take 11/10: divide 11 by 10 to get 1.10, add 1, and the decimal equivalent is 2.10. If a rival shows 2.15 for the same selection, the second bookmaker is offering a better return, full stop. On a £20 stake the difference is £1 in returned profit, which sounds small until it is repeated across a season of bets. The same logic applies to 5/2, which converts to 3.50, and to evens, which is 2.00 in decimal.
Comparing prices is where the arithmetic pays for itself. A few habits make the process reliable:
- Convert every fractional price to decimal before comparing, and never compare a fraction against a decimal directly.
- Check the each-way terms or place odds separately, since these are often quoted in fractional form even when the win market is decimal.
- Compare across at least three bookmakers for the same market rather than settling for the first price you see.
- Factor in any betting promotions or free bet tokens, because a slightly shorter price with a £10 free bet attached can beat a longer price without one.
Comparison tools do the conversion work for you. BestOdds UK is built for exactly this job, pulling prices from multiple operators into a single view so that 6/4 and 2.50 sit side by side as the same 2.50. The site operates under UKGC licence 66479 and accepts Apple Pay, with a £5 minimum deposit. Promo code bop20x10fb unlocks a £10 free bet, and promo code bop5x50fs unlocks 250 free spins, both of which are easier to evaluate once you can read the underlying prices in one format. A bookmaker offering the best price on the market and a welcome offer on top is a different proposition from one offering only one of the two.
The discipline is simple: pick decimal as your working format, convert before you compare, and treat every price as a stake-inclusive return. That single habit closes the gap that mixed formats are designed, perhaps accidentally, to open.
Using converted odds with free bets and casino bonuses
Bonus money changes the arithmetic because the stake is not always yours to lose. A £10 free bet at decimal odds of 4.00 returns £40 on paper, but most UK operators deduct the stake from free bet winnings, so the cash you keep is £30. Read the same price as fractional odds, 3/1, and the deduction is obvious: £10 at 3/1 wins £30 profit, and the stake never belonged to you. This is why converting prices before you place a bonus bet matters. The decimal figure flatters the return; the fractional figure tells you what actually lands in your balance.
Free spins, bonus terms and the odds you are reading
Casino bonuses carry the same trap in a different shape. A 250 free spins welcome offer is usually valued at a fixed spin stake, often 10p, so the spins carry £25 of wagering value, not £250. Winnings from those spins typically face a wagering requirement of 30x to 40x before withdrawal, and table games, Megaways slots and jackpot games are often weighted differently, sometimes excluded entirely. The odds on each spin are set by the game’s return to player, not by a bookmaker, so the conversion skill shifts to reading the terms: spin value, wagering multiplier, maximum win cap and expiry.
Where a sportsbook free bet and a casino bonus sit in the same account, keep the two calculations separate. For the £10 free bet, convert the decimal price to fractional, subtract one, and multiply by ten to see the real profit. For the spins, multiply the spin value by the number of spins to get the bonus value, then check the wagering requirement against realistic play. A 250-spin package at 10p per spin with 35x wagering needs £875 of staking before any withdrawal, which is a very different proposition from the headline number.
BestOdds UK lists a £10 free bet unlocked by promo code bop20x10fb and 250 free spins unlocked by promo code bop5x50fs, with a £5 minimum deposit and Apple Pay accepted. The operator holds UKGC licence 66479 and promotes responsible gambling through GamCare and BeGambleAware, so limits and self-exclusion tools sit alongside the offers. Treat every bonus price as a decimal figure first, convert it, then decide whether the terms still make the bet worth placing.
Take one price you have seen this week, say 6/4 on a football match, and run the conversion yourself before you stake anything. Add one to get 2.50, then compare that figure against every other bookmaker’s decimal price for the same market. If a rival shows 2.60, the fractional quote is the weaker price and you know it in seconds rather than guessing. Do the same in reverse with any decimal price you spot on a mobile app: subtract one and convert the remainder back to a fraction, so 3.75 becomes 2.75, which is 11/4. Twenty minutes of this on a handful of markets builds the habit properly.
Then put the habit to work against the bonuses. A £10 free bet unlocked with promo code bop20x10fb returns profit only on the winnings, so at 2.50 decimal you collect £15 clear of the stake. The 250 free spins tied to promo code bop5x50fs need the same treatment: check the wagering requirement and the game weighting before you spin, because a Megaways slot may contribute less than a table game. BestOdds UK holds UKGC licence 66479, accepts Apple Pay and requires a £5 minimum deposit, so the barrier to testing these offers is low. Set a deposit limit before you start, use the GamCare and BeGambleAware tools if betting stops feeling like arithmetic, and treat every converted price as a number to check rather than a reason to bet.