What dobbing means
“Dobbing” is short for Double Or Bust. It's a Betfair Exchange trading approach for horse racing. You back a horse before the race, then leave a lay order in the market at half the price you backed it at. If the horse's price halves at any point during the race, your lay gets matched and you're locked in for a small profit whatever happens next. If the price never halves, the lay doesn't get matched and you're left with an ordinary back bet, which usually loses.
So it's a bet on the price movement rather than on the result. You don't need the horse to win, you need it to look like it might win at some point, for long enough that the market halves its price. That's why so many in-running watchers like it: a horse that travels well into the straight and then folds is a good outcome for a dobber.
The name oversells it. A matched dob makes roughly one stake before commission, and an unmatched one loses the stake, which happens a lot. This site exists to put numbers on how often that price halving has actually happened.
A worked example
Say you back a horse for £10 at 6.0 before the off, then place a lay at 3.0 (half of 6.0). To balance the position, the lay stake is twice the back stake: £20.
Lay £20 @ 3.0 → loses £40 if it wins, wins £20 if it loses
Lay matched, horse wins: +£50 − £40 = +£10
Lay matched, horse loses: −£10 + £20 = +£10
Lay not matched, horse loses: −£10
Lay not matched, horse wins: +£50 (rare, see below)
Betfair takes commission on your net winnings in a market, so the “+£10” outcomes are really a bit less than £10. Your commission rate depends on your account.
The last line is rare because a horse that wins nearly always trades at 1.01 or close to it in the final strides. In our data, 99.6% of winners with a BSP of 2.02 or more traded at half their BSP or lower in-running. So in practice it's “double or bust”: you either get roughly your stake back as profit, or you lose it.
Why half, and the break-even maths
Laying at half the back price with twice the stake makes the two matched outcomes equal, which is the whole point: once the lay is matched you don't care who wins. You could pick a different exit (laying at a third of the price, say) but then the outcomes are no longer balanced and it's a different strategy.
Here is the uncomfortable bit. If a matched dob makes about one stake and an unmatched dob loses one stake, you need the lay to be matched more than half the time just to stand still. Commission pushes that bar a little higher. That's simple arithmetic, not a prediction, and it's the single most important thing to understand before you look at any of the rates on this site.
How often runners hit half their SP
We checked every UK and Irish win market in Betfair's free Starting Price files between 9 Nov 2025 – 9 Nov 2026. Of 115,385 runners with a Betfair SP (BSP) of 2.02 or more and a recorded in-play price, 32.5% traded at half their BSP or lower at some point in the race. Among the 103,733 that went on to lose, 25.0% still got there.
The biggest single factor is price, though not in the way most people expect. The rate is highest at the two ends of the market: 40.4% for runners priced 2.02–3.95 and 43.6% for 100+ shots, with a dip to 26.6% at 8.0–15.9. Short-priced horses are often in contention, so the market halves their price. Big outsiders are a different story, which we unpick in the starting price guide.
DOB rate by Betfair SP band, all UK & Irish racing
n=10,492
n=23,741
n=26,571
n=20,878
n=19,334
n=14,369
Code matters too. Over the same period the rate was 30.3% (21,599 of 71,175) on the Flat, 35.5% (9,961 of 28,055) over hurdles, 36.7% (4,605 of 12,532) over fences and 37.6% (1,362 of 3,623) in bumpers. You can drill into courses, race types, distances and individual horses from here.
What the numbers can't tell you
This is a tracker of what happened, and it has real limits. Please read them before reading anything into a rate.
- BSP isn't the price you'd get. We measure halving against the Betfair Starting Price. A dobber backs at whatever price is available before the off, which can be higher or lower.
- The in-play low isn't tick-perfect. Betfair's IPMIN figure only counts bets with a payout over £100, so tiny trades at a lower price aren't included. See the methodology.
- Traded isn't the same as matched for you. A price trading doesn't mean every lay at that price got filled. There's a queue, and it can move fast.
- We don't know when. Version 1 shows whether the price halved, not whether it happened in the first furlong or the last.
- The past doesn't repeat on cue. A course or race type with a high rate last year can be different this year. These are historical frequencies, not tips.
Where to go next
If you're new to this, read how starting price changes the picture next, then have a look at race types and courses. If you'd rather check the raw numbers yourself, here's how to read Betfair's files.
By The DoubleOrBust Team · Data 9 Nov 2025 – 9 Nov 2026, updated daily from Betfair's BSP files · How we count