Backing and Laying on Under/Over Markets

Hi all,

Forum newbie here, however I got in to matched betting some years ago, but stopped after the main welcome bonuses dried up. Looking to get back in to it now

I have a question about the back and lay odds on the under/over football markets on exchanges.
Today I was looking to minimise my losses on a rollover bet and found that the Under/Over 2.5 goal market for a football match was the best option.

The bookie was offering a back bet of 1.97 on the match finishing under 2.5 goals.
Smarkets was offering 2.04 on a lay bet of the match finishing under 2.5 goals.

No probs so far…

However on the exchange I noticed that the back bet of the match finishing OVER 2.5 goals was taking bets with sufficient liquidity for my bet with odds of 1.97 also.

Now this is probably a simple answer, but I just wanted to clear things up to be sure. If I backed UNDER 2.5 goals on the bookies site, and OVER 2.5 goals on the exchange, is this the same as laying the bet on the UNDER exchange market?

It seems to me that it would be, but the fact that the odds were different for each made me question myself and go for the lay option with slightly higher odds (therefore a greater overall loss).

Could anyone shed some light on why these odds would have been different, and how it would affect future bets that I place? Also any quirks about how the money comes out that might affect any calculations in stake.

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2ttc
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April 4, 2017 at 12:41 pm

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Ox 0 April 4, 2017 at 3:17 pm

Yes, once you have backed ‘Under 2.5’ at the bookie then you can choose to either lay ‘Under 2.5’ or back ‘Over 2.5’ on the exchange.

Laying at odds of X is equivalent to backing the opposite outcome at odds of 1/(1-1/X), so in your example laying ‘Under 2.5’ @ 2.04 is equivalent to backing ‘Over 2.5’ @ 1.96, so you would have been (very slightly!) better off backing ‘Over 2.5’ @ 1.97 directly.

The difference can be attributed to the overround on the selections at the time you place your bet; if the lay book is a long way under 100% but the back book is closer to 100% then you will be better off backing, and the other way round when the back book is far over 100% but the lay book is close to 100%.

When the market is fully formed (ie both sides are close to 100%) then having to place bets at odds intervals defined by the exchange (ie you can back at 2 or 2.02 but not at anything in between) means these tiny differences will always exist.

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Ox 0 April 4, 2017 at 3:39 pm

Just to clarify: if you are laying at odds of X with a liability of £Y, that is the same thing as backing the opposite outcome with £Y @ 1/(1-1/X)

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feltt1p 5 April 4, 2017 at 4:35 pm

This is dutching, not a simple back and lay. See oddschecker dutching calculator.

For your purposes, say I was on 3/1 for under 1.5 goals in Man U/Everton. The lay is 4.1, whereas the back on over 1.5 is 1.35. So it’s obviously not the same scenario.

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2ttc 0 April 4, 2017 at 5:50 pm

Thanks a lot for your help replies, I’ll look in to it!

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MaxBettor 0 December 27, 2023 at 7:31 pm

How comes the odds for laying an Under X goals can be so different than the odds for backing Over X goals if they effectively mean the same thing?

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