If you only bet with traditional bookmakers, you’re dealing with one set of odds. The bookie sets a price, you take it or leave it. Betfair and the betting exchanges work differently, and Betfair SP (Starting Price) is a specific feature worth understanding, because it can be better value than what the bookmakers offer — sometimes significantly so.
How Betfair works (briefly)
Betfair is a betting exchange. Instead of betting against a bookmaker, you’re betting against other people. Someone offers odds on a horse (the “layer”), and someone accepts those odds (the “backer”). Betfair takes a commission on winning bets, typically 5% of your profit, though this decreases with volume.
Because the market is driven by supply and demand between thousands of participants, exchange odds tend to be closer to the “true” probability of an outcome. There’s no bookmaker margin baked in. The trade-off is that you pay commission on winnings, and the odds can be volatile — they move right up until the off.
Exchange odds are quoted in decimal format on Betfair (2.0 = evens, 3.0 = 2/1, 11.0 = 10/1), though you can switch the display to fractional.
What Betfair SP actually is
Betfair SP is the starting price generated by the Betfair exchange at the moment a race starts. It’s calculated from the state of the exchange market — the unmatched back and lay orders that are sitting in the system when the race goes off.
It’s not the same as the industry SP (ISP) you see in the Racing Post or on results pages. The industry SP is determined by on-course bookmakers’ boards. Betfair SP is determined by exchange activity.
You can request BSP when placing a bet on Betfair. Instead of taking a specific price, you say “I want to back this horse at whatever the Betfair SP turns out to be.” Your bet gets matched at the off.
The advantage is convenience — you don’t need to be watching the market and timing your bet. The disadvantage is that you don’t know your exact odds until the race starts.
How BSP compares to bookmaker prices
This varies by race and by horse, but there are some general patterns.
On favourites and short-priced horses, BSP is almost always better than bookmaker prices. Bookmakers build their margin into every price, and it’s most noticeable on favourites. A horse that’s 2/1 with bookmakers might be 2.15 (roughly 23/20) on BSP after commission. Over hundreds of bets on favourites, this difference adds up substantially.
On big outsiders, the picture is mixed. BSP can be bigger than bookmaker prices on genuine outsiders because the exchange market sometimes drifts those horses to huge prices. But it can also be shorter if there’s late money for the horse on the exchange. It’s less predictable at the extremes.
On the morning of a race, bookmaker early prices are often more generous than what BSP eventually settles at, particularly for horses that attract support. If you take 8/1 with a bookmaker in the morning and the horse opens at 5/1 on course, BSP might be 5.5 or 6.0 — worse than your early price. But if the horse drifts, BSP might be 12.0.
As a rough rule: if you’re backing a horse that you expect to shorten (be popular in the market), take the best bookmaker price early. If you’re backing one you expect to drift, BSP can be a good option.
The commission factor
Betfair takes commission on your net winnings, not on every bet. The standard rate is 5%, though it reduces based on your Betfair Points (effectively a loyalty discount). High-volume users can get it down to 2-3%.
This commission is already factored into BSP returns. When Betfair quotes a BSP of 8.0, that’s before commission. Your actual return is 8.0 minus 5% of the profit. So on a £10 bet at BSP 8.0, you’d win £70 profit before commission and pay £3.50 commission, netting £66.50. Your effective odds are about 7.65.
You need to account for this when comparing BSP with bookmaker prices. A bookmaker offering 7/1 (8.0 in decimal) with no commission is slightly better than BSP 8.0 with 5% commission. But if BSP is 9.0 and the bookmaker is 7/1, BSP wins even after commission.
Best Odds Guaranteed (BOG)
Most major bookmakers offer Best Odds Guaranteed on UK and Irish horse racing. The deal is simple: if you take a price with the bookmaker and the official industry SP is bigger, you get paid at the SP instead.
So if you back a horse at 6/1 and the SP is 10/1, you get 10/1.
This is a genuinely good offer for punters and it changes the calculus on when to bet. With BOG, taking an early price has no downside — if the horse drifts, you get the bigger price anyway. If it shortens, you’ve locked in the better price.
BOG is one of the main reasons bookmaker accounts have value despite their built-in margins. If you can combine BOG with strong early prices, you frequently end up with better effective odds than BSP.
The catch: bookmakers will restrict or close accounts that consistently beat them. If you’re always taking early prices on horses that shorten (suggesting you have information or good judgement), the bookmaker will eventually limit your stakes. This is one of the main reasons profitable punters end up on Betfair — the exchange doesn’t restrict winners.
When to use BSP versus bookmakers
Use BSP when:
You’ve been restricted by bookmakers (this is the main reason most people end up on the exchange). You want to bet on a horse that you think will drift in the market. You’re backing at shorter prices where the exchange margin is tighter than the bookmaker margin. You want guaranteed execution — BSP bets always get matched, whereas trying to get a specific exchange price might not.
Use bookmaker prices when:
You’re getting BOG and you think the horse might drift. You’ve found a bookmaker offering a clearly better price than the current exchange market (this happens, especially in the morning). You want each-way terms, which Betfair doesn’t offer in the same way (Betfair has a separate place market, which is actually often better value — but it’s a different bet structure).
Use specific exchange odds when:
You’re an experienced exchange user and you can see value at a specific price in the market. You want to trade in and out of a position (backing at one price and laying at another to lock in profit). You want to lay a horse (bet against it), which bookmakers don’t offer at all.
BSP and the industry SP: which is better?
Studies over large samples have consistently shown that Betfair SP is a more efficient market than the industry SP. The industry SP is set by on-course bookmakers who are influenced by crowd behaviour, by what prices other bookmakers are showing, and by the desire to balance their own books. The exchange SP is set by a much larger pool of participants with a wider range of information.
In practical terms, this means BSP tends to be more “accurate” as a predictor of outcomes. Horses at shorter BSP win more often than horses at the same industry SP. The exchange market is harder to beat consistently, because it’s a more efficient market.
For punters, this cuts both ways. A more efficient market offers fewer opportunities for big mispricings, but it also means you’re less likely to take a terrible price. If your main concern is not getting ripped off, BSP is a solid baseline.
A practical workflow
If you have both bookmaker accounts and a Betfair account (and you should), a reasonable approach looks like this:
Check the exchange market for a horse you want to back. Note the current price. Then check the bookmaker prices. If a bookmaker is offering better odds than the exchange (this happens surprisingly often in the morning), take the bookmaker price with BOG. If the bookmaker prices are worse than the exchange, either take a specific exchange price or request BSP.
Keep a record of what you back and at what odds, and periodically compare your achieved prices with what BSP was. Over a few hundred bets, you’ll see where you’re getting the best value and can adjust.
The goal is always the same: get the best possible odds on whatever you’re backing. Sometimes that’s a bookmaker, sometimes it’s the exchange, sometimes it’s BSP. Being flexible about where you bet, rather than loyal to one platform, is worth real money over time.