Cross Match by BETFAIR

[mickyxx1]

HI there, can anyone explain to me how betfair's CROSS MATCH works on horse racing in play, i understand it for Tennis or Cricket as explained on there website when there are two selections in the event but i can't get it on horse racing. Sorry in advance for my novice betting knowledge.

[GaryRussell]

We used this explanation to program the calculation in Betting Assistant. Sorry I cannot explain it better then explained here (maybe someone else can). It is an example where there are three outcomes, but the same principle applies to any number of outcomes.

http://bdp.betfair.com/index.php?option ... &Itemid=62

[Graham]

The way I work out the cross match price is basically the price which will make a 100% book on the other side - backing is simply laying all the others and vice versa.

You can calculate it by working out the percentage of the book which the other runners form.

The calculation is quite simple - take the sum of the inverse of all the other runners on the other side (ie the lay prices if you are backing and vice versa).

Subtract this from one, then calculate the inverse.

As an example, take the following four runner field:

----------- BACK LAY
HORSE A 1.2 1.21
HORSE B 8 10
HORSE C 18 20
HORSE D 100 200

If you are backing B then work out the percentage of the book that the other runners make up on the lay side

1/1.21+1/20+1/200=0.881446281

Subtract this from 1 to get 0.118553719

Cross Match odds to back B: 1/0.118553719=8.434994772


If you want to calculate how your stake is split (and you want a headache!), you need to take your potential return, and use that as the basis of your payout figure for the other runners

For example backing B for £300 gives you a payout of £300*8.434994772=£2530.50

You will then be laying as follows:
A: £2530.50/1.21 = £2091.32
B: £2530.50/20 = £126.52
C: £2530.50/200 = £12.65

TOTAL LAYS £2230.50 (penny rounding error)

This gives you a loss of £300 if B loses and a profit of £2230.50 if B wins.

However (if you haven't got a headache already!) you won't get odds of 8.434994772. Instead betfair only offer odds of 8.4. This would give you a return of £2520, £10.50 less than the true cross match return.

Betfair could either match to £2520, which would mean lays of 2082.65, 126, and 12.60 respectively on A B and C, meaning that of your £300 betfair need only risk £298.75, therefore "skimming" £1.25 from your stake, or simply retain the additional profit of £10.50 should you win, which is, of course, the £1.25 at odds of 8.4.

This, of course, is only correct if there are sufficient amounts on the opposite side, I am assuming in this example that there are.