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How to calculate lay odds

S

SHARPYWAN

Yearling
Hi, Sorry if i'm being a little thick here.
I'm looking to lay a number of events, but struggling to figure out my odds.
So if i have a number of events that i know only have a 10% chance of occurring, i want to lay them to make a 20% profit (assuming those % play out)
, what odds do i therefore need to offer, and what is the formula (excel ideally) for this please, as other events will have a slightly different % i.e. 12% chance.

Many thanks
Richard
 
In above example, on an event with 10% chance of occurring, you will need to offer odds of 15/2 (8.50 in decimal odds) for a 20% profit.

The formula used is as follows

=((100/10)-1)/1.2

This will give you fractional odds, simply add +1 at end of above formula to get decimal odds.

In the formula 10 is percentage chance of event occurring, you can change this to 12 or whatever the chance of event is. 1.2 comes from 1 total probability plus 20% profit/overround, for example if you were looking for 15% or 25% profit you will change this accordingly to 1.15, 1.25 etc. Note the brackets in formula are very important and should be used correctly.

If as you say, you will need to change chance % often, it’s best to change the percentage in a different cell in excel and have the formula refer to it, as it’s good practice not to edit formula cell often to avoid accidental mistakes.

So in excel, type your chance percentage in cell A1 for example, then have formula in cell B1 as follows

=((100/A1)-1)/1.2+1

Above will give you the decimal odds (because of +1 added at the end)

You can test that above formula is correct if following equation is true

Chance x fractional odds offered x 1.2 = 100 - chance

I hope this helps.
 
Many thanks for that much appreciated.
I still don't seem to be able to get this right.
Example: i want to lay the event.

So i have a football match that the home team will win 80% of the time.
I want to lay the away team.
So using what you suggest above would mean i would offer odds of 4.33 (rounded to 4.3 on betfair) to make 20% profit.

So if this event happens 100 times and i lay it 100 times at £10, my liability is £1000
I will then have:
80 wins @ £3.03 (£10 at 4.3 odds) = £242.40
20 losses @ £10 stake = £200
Profit of £42.40 from £1000 bets
= only 4.24%, not 20%

I am confused, can anybody help please
Thanks
 
Ah I see, you are looking for 20% profit on total liability. I like maths, but it is a long time since I left school haha, so had to think about it. I think the following formula should work for what you are looking for (I hope).

=chance of not happening/(chance of happening+Profit required)+1

Above should give you decimal odds to lay

For example if you are laying an outcome that has 10% chance of happening then it would be =90/(10+20)+1 which should return 4.0 decimal odds which is equal to 3/1. Try it for other possibilities, hopefully it should work.
 
That's great thank you, believe it or not i did A level Maths and i'm a qualified accountant lol. Just couldn't get my head around it. Thanks for your help, much appreciated :)
 
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