Betting odds explained for Grand National 2027
Last Updated 1 week ago | By The GrandNational.org.uk StaffPlenty of people pick their Grand National horse based on a name they like or a set of colours that catch the eye, and there’s nothing wrong with that. But it still helps to know what the odds beside each horse actually mean.
In short, betting odds tell you two things – how likely the bookmaker thinks an outcome is, and how much you’ll get back if it happens. That applies whether you’re backing a horse at Aintree, your favourite football team on Saturday afternoon or a party at the next election.
Fractional betting odds explained
Fractional odds are the traditional format you’ll see on the boards at racecourses and in betting shops. They show what you’ll win relative to what you stake. The number on the left is your profit, and the number on the right is the stake it relates to.
Fractional odds explained – an example
Say a Grand National runner is 10/1. That means £10 of profit for every £1 you stake. Put £5 on and, if your horse wins, you get £50 in winnings plus your £5 stake back, which means a return of £55 in total.
Decimal betting odds explained
Decimal odds are the standard across much of Europe and you can switch to them at any online bookmaker. Most people find them simpler, because there’s only one sum to remember: stake multiplied by odds = total returned.
Decimal odds explained – an example
Take the same horse. In decimal, 10/1 is shown as 11. A £5 stake gives you £5 x 11 = £55, exactly the same as the fractional example above. The difference is that the decimal figure already includes your stake, which is why it’s 11 rather than 10.
Decimal and fractional odds converter
The table below shows how fractional and decimal odds line up, along with the approximate probability each price implies.
| Fractional odds | Decimal odds | Percentage probability |
|---|---|---|
| 1/2 | 1.5 | 67% |
| Evens | 2 | 50% |
| 6/4 | 2.5 | 40% |
| 2/1 | 3 | 33% |
| 3/1 | 4 | 25% |
| 4/1 | 5 | 20% |
| 5/1 | 6 | 17% |
| 6/1 | 7 | 14% |
| 8/1 | 9 | 11% |
| 10/1 | 11 | 9% |
| 12/1 | 13 | 8% |
| 14/1 | 15 | 7% |
| 16/1 | 17 | 6% |
| 20/1 | 21 | 5% |
| 25/1 | 26 | 4% |
| 33/1 | 34 | 3% |
| 50/1 | 51 | 2% |
| 100/1 | 101 | 1% |
How are the odds for each Grand National horse decided?
Several things feed into the price you see next to each horse. The final Grand National runners aren’t confirmed until two days before the race, but you can bet a long time before that through the ante-post market, which covers the horses bookmakers expect to line up.
Bookmakers compete for your custom by setting their odds as attractively as they can. It’s not so different from any other kind of shopping. There’s no reason to pay £50 for a pair of trainers if the same pair is £40 further down the high street.
Prices aren’t plucked out of the air, though. If a horse attracts a lot of money, bookmakers will shorten its odds to limit what they’d have to pay out. If nobody wants to back it, the price drifts out. That push and pull is why the market keeps moving right up until the off.
Grand National Festival – Aintree Racecourse, Liverpool, Britain – April 12, 2018. Might Bite ridden by Nico de Boinville in action (R) before winning the 14:50 Betway Bowl Chase. Action Images via Reuters/Jason Cairnduff TPX IMAGES OF THE DAY @SCANPIX
Betting at Aintree racecourse
The bookmakers you see at the track are known as rails bookmakers, lined up in rows in front of the grandstand. The area is sometimes called the betting jungle, and on Grand National day it’s busy, loud and a bit bewildering if you’ve never done it before.
Odds move quickly down there as each firm competes and adjusts its position. If a lot of money arrives for one horse, they’ll cut its price. It’s worth a go if you’re at the course: have your horse’s number and your stake ready, and you’ll be fine. The rails bookmakers are old-school racing people and dealing with them is part of the day.
Ante-Post Betting
An ante-post market is simply betting on a race well in advance. Bookmakers price up the Grand National months ahead, which lets you get on at a bigger price than you’ll find in April.
The trade-off is risk. If your horse doesn’t make the final field of 34, you normally lose your stake, and with an entry list of around 80 in February that happens often enough. The way round it is to look for Non-Runner No Bet, a promotion that refunds your stake if your selection doesn’t run. Weighing the bigger price against that risk is the whole art of ante-post betting.
For current prices and analysis, see our Grand National ante-post outlook for 2027.
Understanding the over-round
Every betting market has what’s called an over-round, and it’s how bookmakers make their money.
If you add up the implied probability of every horse in a race, a market at exactly 100% would be break-even for the bookmaker. In practice it’s always higher, and the difference is their margin.
- In a race the size of the Grand National, with 34 runners, the over-round is typically somewhere around 125-150%
- Anything above 100% represents the bookmaker’s potential profit on the race
- At an over-round of 120%, a bookmaker would expect to pay out roughly £100 for every £120 taken
Markets with fewer runners tend to be tighter, and with so many firms competing these days you’ll occasionally find small-field races priced very close to 100%.
15 minutes before the Grand National all bookmakers will have the same odds
In the build-up to the race it’s well worth shopping around, because prices differ from one site to the next. Why take 10/1 if another bookmaker is offering 12/1 on the same horse? On a £10 bet that’s £20 of extra winnings for no extra outlay.
Roughly 10 to 15 minutes before the race gets underway, the market moves into what’s known as the live show. From that point every bookmaker in the country quotes the same price on each horse, so there’s nothing left to shop around for. If a horse is 10/1 on the live show, it’s 10/1 everywhere.
Money coming in at the track can still move things, so a horse at 10/1 might be backed into 8/1, but that shift applies across every betting shop and website at once. Whatever price a horse is returned at becomes its SP, or starting price, which is why the results look identical wherever you read them the next morning.
Importantly, if you took a bigger price earlier in the day or weeks before, the bookmaker honours the price you took.
Tip: look out for Best Odds Guaranteed. If you take a price and the horse goes off at a bigger one, you get paid at the bigger price. Back one at 8/1 and see it return 10/1, and you’ll be paid at 10/1.
Tips and hints before placing your Grand National bets
A lot happens in the build-up, but the market really comes alive on the morning of the race and in the hour before the off.
The weather is the big one. Some horses need soft ground and others want it quick, so a wet week at Aintree can reshape the whole market. A well-fancied horse who wants a sound surface will drift if the rain comes, while the mudlarks in the field shorten as punters cotton on.
The classic example came in 1998, when Earth Summit was available at 20/1 or bigger on the morning of the race. A deluge turned the ground heavy, which was exactly what he wanted and precisely what most of his rivals didn’t, and he was backed into 7/1 favourite by the off. He duly won, and the bookmakers were still paying out the next day.
Trainers and jockeys matter too. Willie Mullins has won the last three Grand Nationals and any horse he sends over will attract support on that basis alone, while leading riders like Paul Townend and Sean Bowen always have their followers regardless of the horse.
Course form is worth a close look as well. I Am Maximus has won twice in three years with a second place in between, while Iroko followed up his fourth in 2025 by finishing runner-up in 2026. Horses who have merely run well over these fences are often worth another chance. The obstacles and the trip suit a particular type, and once a horse proves it handles them, that tends to hold.
Useful Grand National betting links and ‘how to’ guides
Now you have a better idea of what odds look like and how they can change, you can bet on the Grand National with confidence. Head to our Grand National runners page, which includes the latest betting ahead of this year’s Grand National Festival. Once you’ve decided on your Grand National bets, the easiest way to place them is from the comfort of your own home, making the most of generous offers and free bets by betting online. If you want even more information about betting on the Grand National, take a look at our complete betting guide, which is linked below.
Download our Grand National Betting Guide
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The GrandNational.org.uk Staff
