Betfair SP explained: how BSP is calculated and used

How is Betfair SP calculated?

At the off, Betfair takes all the SP back bets and SP lay bets for each runner, matches them against each other and against the unmatched orders left in the normal exchange market, and returns the price that balances them as the BSP.

The reconciliation happens as the market is suspended at the start. If SP backers want more money matched than SP layers can cover, the unmatched lay orders waiting in the exchange are used to fill the gap, and the BSP settles at the price that allows the most money to be matched fairly. Everyone matched at BSP gets the same price, whatever their stake.

Because it comes from the exchange market, BSP reflects prices set by backers and layers rather than by bookmakers. It is returned in decimal odds, often to two decimal places, and it can land between the normal exchange price steps.

What is the difference between limit on close and market on close?

A market on close bet accepts whatever BSP is returned, while a limit on close bet sets a price limit, a minimum for backers or a maximum for layers, and is matched only if the BSP is at or better than that limit.

Market on close is the simple option: you will be matched at the BSP, whatever it is. Limit on close protects you from a price you do not want, such as backing a horse you would not take at shorter than 5.0, but it risks not being matched if the horse is well backed and the BSP falls below your limit. Both types can be placed well before the off and left in the market.

How does commission affect a Betfair SP return?

Exchange commission is charged as a percentage of your net winnings in each market, so a winning BSP bet returns slightly less than the price suggests, and commission is only paid when you win overall in that market.

If you back a horse at a BSP of 6.0 and it wins, your gross profit is five times the stake, and commission is deducted from that profit. Because the rate applies to net winnings per market, a bet that loses costs nothing extra. When comparing BSP with a bookmaker's price, knock the commission off the profit part of the exchange price first.

Is Betfair SP bigger than the industry SP?

Usually, yes, for horses beyond the first few in the betting, because exchange prices carry little built-in margin while bookmakers load their margin onto outsiders, but for short-priced favourites the two are often close.

A horse returned at 20/1 industry SP, which is 21.0 in decimal, can easily have a BSP of 30 or more. The bigger the price, the wider the gap tends to be. For favourites the difference is small, and once commission is taken off the exchange winnings, a bookmaker's price or a best odds concession can be as good. The BSP table on this page shows win rates by BSP band in British and Irish racing since March 2024.

The comparison matters when judging past prices. A horse that started at 16/1 with a BSP of 30 was more friendless in the market than the SP alone suggests, while one with a BSP close to its SP was supported on both sides of the market.

How do you lay a horse at Betfair SP?

Place a lay SP bet by setting your maximum liability, and at the off it is matched at the BSP, so the stake you have laid is that liability divided by the BSP minus one.

If you set a liability of £40 and the BSP is 5.0, you have laid a £10 stake: you pay £40 if the horse wins and keep the £10, minus commission, if it loses. Setting the liability rather than the stake means a big outsider cannot create an unexpectedly large loss, and a limit on close bet also lets layers set a maximum price.

Where does Betfair SP appear in form data?

Many results databases store the BSP beside the industry SP for every runner, which lets analysts compare the two prices, study market strength and build statistics on exchange prices as well as bookmaker prices.

For past-performance analysis, the SP is the traditional reference and the BSP gives a second view with less margin. Neither is right or wrong: use one consistently. If you are comparing a horse's past prices, BSP shows more clearly how big outsiders really were, while the industry SP is the price most bets and statistics are settled on.

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