Lay odds formula

[Insibibious]

Just wondering if anyone has an excel formula to work out the real lay odds on Betfair? i.e. If I lay £100 at 2, it's not really 2, it's actually a little more than that due to commission.

Thanks!

[Wednesday 13]

If you have Lay Odds in cell A1, and commission, in %, in cell A2, formula is:

=(100*A1-A2)/(100-A2)

I.e.,

Actual Lay Odds = (100 * Lay Odds - Commission) / (100 - Commission)


Here is simple maths:

Lay Odds = Return / Profit = (Liability + Profit) / Profit

"Profit", I mean your actual winnings, what you put in your pocket, which is Backer's Stake minus Commission; so you can say

Actual Lay Odds = (Liability + Actual Profit) / Actual Profit

Since commission is expressed as %, you have:

Actual Profit = (1 - Commission/100) * Stake

Liability = (Lay Odds - 1) * Stake

So we have:

Actual Lay Odds = (Liability + Actual Profit) / Actual Profit =

= ((Lay Odds - 1) * Stake) + (1 - Commission/100) * Stake) / ((1 - Commission/100) * Stake) =

= (Lay Odds - Commission/100) / (1 - Commission/100), which is rearranged into above formula.

So, in your example, laying at odds of 2.00 with 5% commission, one actually lays at 2.053.

[Insibibious]

If you have Lay Odds in cell A1, and commission, in %, in cell A2, formula is:

=(100*A1-A2)/(100-A2)

I.e.,

Actual Lay Odds = (100 * Lay Odds - Commission) / (100 - Commission)


Here is simple maths:

Lay Odds = Return / Profit = (Liability + Profit) / Profit

"Profit", I mean your actual winnings, what you put in your pocket, which is Backer's Stake minus Commission; so you can say

Actual Lay Odds = (Liability + Actual Profit) / Actual Profit

Since commission is expressed as %, you have:

Actual Profit = (1 - Commission/100) * Stake

Liability = (Lay Odds - 1) * Stake

So we have:

Actual Lay Odds = (Liability + Actual Profit) / Actual Profit =

= ((Lay Odds - 1) * Stake) + (1 - Commission/100) * Stake) / ((1 - Commission/100) * Stake) =

= (Lay Odds - Commission/100) / (1 - Commission/100), which is rearranged into above formula.

So, in your example, laying at odds of 2.00 with 5% commission, one actually lays at 2.053.

Fantastic Wed. 1000 thank yous!