trading formulae

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there must be a quick formulae for trading in running.what i am after for arguement sake is for example, i have £20 on a 2.5 shot (6/4) and i want to make £5 profit in running if it hits the low enough odds win or lose.
you can play around with the "what if" on betfair to get all the selections green but i would rather use a formulae as it would be quicker.

[mathare]

So you have £20 on at 2.5 giving you a potential profit of £30 (excluding commission)./ You want £5 profit win or lose, right? You want to lay at lower odds than 2.5 (obviously).

Your profit if the horse wins, in general terms is.:
(back_stake * (back_odds - 1)) - (lay_stake * (lay_odds - 1)), i.e. backing profit - laying liability
If the horse loses your profit is
lay_stake - back_stake
So use this formula to set your staking ratios, based on the target profit you want to achieve. You can then rearrange the first formula to find the odds you would need to lay at to achieve this profit...

To get the same profit whether the horse wins or loses you need the product off the decimal odds and stake for both the back and the lay to be the same. So in your example you've backed for £20 at 2.5 which gives a product of 50. So lay_stake * lay_odds must be 50 too to guarantee the same profit win or lose. You want a £5 profit so your lay_stake must be £25 which means your odds must be 2.0.

In general terms then:
lay_stake = back_stake + target_profit
lay_odds = (back_stake * back_odds) / lay_stake

Does that make any sense?

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i can see what you are saying matt but i dont think i fully understand it.
what i want to make is a 25% profit on any number of horses in a race.
if i see the first 2 in the betting and they are for example
2.5
3.9
lets just say i got about 2 minutes to bet and i got £30 on both, i need to act fast and know how much to lay to win £7.50 on each
i just want to know how much to multiply or divide on stake and odds

[mathare]

i can see what you are saying matt but i dont think i fully understand it.OK, let's work through these examples...


what i want to make is a 25% profit on any number of horses in a race.I'm assuming this is 25% profit on each runner, not on the race in total...


if i see the first 2 in the betting and they are for example
2.5
3.9
lets just say i got about 2 minutes to bet and i got £30 on both, i need to act fast and know how much to lay to win £7.50 on each
i just want to know how much to multiply or divide on stake and oddsTo win £7.50 on each your laying stake has to be £37.50 - that's a given. If the horse loses then you lose your backing stake and win the laying stake so the laying stake has to be £7.50 higher than the backing stake.

What you need to know is the odds you can lay at to guarantee this profit. To get these:
* multiply back_stake by back_odds, e.g. £30 * 2.5 = 75
* divide above by lay_stake to get lay_odds, e.g. 75 / 37.50 = 2.00
So if you have backed the first runner at 2.5 for £30 then to guarantee £7.50 profit you need to lay it at 2.00 for £37.50.
You can do the same calculations for the second runner and see you need to lay that one at 3.12 for £37.50

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thank you matt

[mathare]

thank you mattI assume it made sense then :)

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yip