What Bet Size Effects Win Odds?

[InFront]

Is there a formula where you can determine at what bet size for win wagers starts to effect odds based on the size of a win pool? For example say at a small track there was only $5,000 in the win pool how much can you really bet safely without destroying your odds? Of course if you are mainly a longshot player smaller bets can effect odds more easily but let's say your average odds on all plays (winners and losers) were 4/1 and the average win pool was $5,000 is there a basic formula to find out what size win bets can you make safely?

[CBedo]

The math is pretty straight forward actually. You just need to know the takeout percentage for the track's win bets. Since you know the total pool size and the amount bet on the horse in question, you can see what adding a certain amount does to the odds, or you can reverse it and see how much would it take to drop the odds by some set amount. I've got 10 things going right now, or I'd write out the formulas, but if noone else does, I'll do it for you in a bit if you need it.

[InFront]

The math is pretty straight forward actually. You just need to know the takeout percentage for the track's win bets. Since you know the total pool size and the amount bet on the horse in question, you can see what adding a certain amount does to the odds, or you can reverse it and see how much would it take to drop the odds by some set amount. I've got 10 things going right now, or I'd write out the formulas, but if noone else does, I'll do it for you in a bit if you need it.

Ok thanks. What I was looking for is some basic formula to get an "idea" what win bet size may be too much. For example I don't want to have to say ok there is $7,000 in this exact pool and the track take on win is -18% and my horse is currently at 6/1, etc. What I like to know "in general" for this track if the average win pool size at a track is $10,000 with a track take of -19% and my average post odds of all my plays is 7/1 what is the max size bet on win should I make? Yes in one race my horse may have 15/1 odds while another race only 3/1 so effect things but I'm just trying to get an "overall" size for all my max win bets possible?

And of course the higher your roi% is the more you can afford to bet and change odds but let's say just a basic +10% roi what size win bets really start to effect it? Thanks.

[dvlander]

InFront:

I have a very simple Excel spreadsheet that does exactly what you are asking for in win pools. You have to supply four basic pieces of info:

The size of the entire win pool
The track takeout percentage
The odds on your horse with you OUT of the pool
Your strike rate (or win percentage)
Send me a PM telling me what Excel version you have and I'll be happy to send it your way. The design of the spreadsheet is courtesy of Jeff Platt of JCapper and HANA fame.

Dale

[CBedo]

Here's the simple version:

Before your bet, we have the total win pool (p), the amount bet on your horse to win (w), and the takeout rate (t). So the odds before (Ob)you bet are: Ob = (p * (1-t)) / w) -1.

Now you are going to place a bet (b) on your horse, so the odds after (Oa) will be: Oa = (((p+b) * (1-t)) / (w+b)) - 1.

If you subtract one from the other, you will get the change in odds (cO) for a certain size bet: cO = Ob - Oa. Now if you plug those in and start reducing all that mess, you get: cO = (1-t) * (b/(b+w)) * ((p-w)/w) which looks ugly, but really isn't. It's what's left after takeout (1-t) times how much your bet is as a percentage of the total bet on the horse (b/(b+w)) times what the no takeout odds were on the horse before your bet ((p-w)/w). If you wanted to see what size bet would reduce the odds by a certain amount, you can just change the equation around and solve for yoru bet size instead of the change in odds.

I hope that makes sense. If not, feel free to ask more questions or pm me. An excel sheet is the way to go for sure (that's why it took me so long to get back to you. I just have it in a sheet, and was too busy to derive it last night).

[InFront]

Here's the simple version:

Before your bet, we have the total win pool (p), the amount bet on your horse to win (w), and the takeout rate (t). So the odds before (Ob)you bet are: Ob = (p * (1-t)) / w) -1.

Now you are going to place a bet (b) on your horse, so the odds after (Oa) will be: Oa = (((p+b) * (1-t)) / (w+b)) - 1.

If you subtract one from the other, you will get the change in odds (cO) for a certain size bet: cO = Ob - Oa. Now if you plug those in and start reducing all that mess, you get: cO = (1-t) * (b/(b+w)) * ((p-w)/w) which looks ugly, but really isn't. It's what's left after takeout (1-t) times how much your bet is as a percentage of the total bet on the horse (b/(b+w)) times what the no takeout odds were on the horse before your bet ((p-w)/w). If you wanted to see what size bet would reduce the odds by a certain amount, you can just change the equation around and solve for yoru bet size instead of the change in odds.

I hope that makes sense. If not, feel free to ask more questions or pm me. An excel sheet is the way to go for sure (that's why it took me so long to get back to you. I just have it in a sheet, and was too busy to derive it last night).

Can you just give one example. Let's keep it simple say at post time there is $10,000 in the win pool, the track take is 20% and my horse has currentlt $1,000 on it. What is a safe amount for me to wager on it?

[Ray2000]

Honestly, I didn't read this thread until after I posted this in harness today

http://www.paceadvantage.com/forum/showthread.php?t=58681

that's spooky


hope it helps

[CBedo]

Can you just give one example. Let's keep it simple say at post time there is $10,000 in the win pool, the track take is 20% and my horse has currentlt $1,000 on it. What is a safe amount for me to wager on it?Sure, sorry if it was confusing.
In your example, p=10000, w=1000, & t=20%. So the odds that would be showing on the board would be 7/1. (With 0 takeout, the odds wold be 9/1).

Now, lets see how much we could bet that would only drop the odds by 1 point for example. So using the last formula we derived, we see plug in some values: 1 for the odds change, 0.8 for (1-t), and 9 for the odds without takeout ((p-w)/w). So we get 1 =0.8 * 9 * b/(b+w). So we are left with our percentage of the total amount bet on our horse which comes out to be just under 14% of the total amount bet on him or about 161 dollars. (if you know the percentage then plugging that in gets you the amount = w*percentage/(1-percentage).

If you just want to see what will happen to the odds if you bet a certain amount, it's easy as well. Lets say you want to bet $100 on this same horse, then plug it in and we get 0.8 * 9 * [100/(100+1000)] which equals about 0.65. So by betting 100 dollars you will drop the odds from 7 to about 6.35.

Again, if any part of this doesn't make sense, keep asking or pm me.

[InFront]

Ok thanks to all who posted or sent me an Excel sheet to work with.