# Shortcut to change percentages above 50% to odds?

Working through Doug's Poker Work Book for Math Geeks and there have been a few exercises where I am calculating for odds that are greater than 1:1 (50%). Whereas I have a good grasp on how to convert back and forth between percentages lesser than 50% (e.g. 33% = 2:1) my brain seems to be running into a wall on anything that is higher than this 1:1 speed bump (i.e. .8:1). Maybe someone out there who is a lot better at math can provide a handy way to do this quickly?

Specific example would be from pg.88 having 72% equity and converting to x:1?

• Red Chipper, KINGOFTAGS Posts: 2,241 ✭✭✭✭✭
edited September 2016
Damn - good Q...
there's a video, I think, where Doug or one of the coaches talks about figuring out this... I will try to look around and see if I can find it.

But one of the quickest methods is just going to the nearest "whole percentage" that's easy for you to figure out... for example, for 72% equity - I'd round it up to 75% which is
3 to 4 (¾ is 75%). If it was 83% - I'd go to 80 which is 4 to 5 (4/5 is 80%).

I think I'm doing it right... lol!
I'll try to dig up that video and you can view it for yourself...

EDIT:
check out "Bracketing" video
• Red Chipper, RCP Coach Posts: 278 ✭✭✭
edited September 2016
It's just the percentage divided by the difference of 100 over 1. So...
72/28 = 2.57
So it's 2.57 to 1.
• Red Chipper Posts: 1,018 ✭✭✭✭
edited September 2016
.8:1 means you win 8 times and loose 1....so the total number of plays is 9

so its 8/9 * 100 or 89% as a formula (i hate formulas but if one must)
(times you win/(times you win+times you loose)) * 100

going the other way its just 89% means you win 89 times out of 100 witch means you loose (100-89) 11 times....so itl's 88/11 which reduces down to 8/1 or 8 to 1

Using Matt example (and he confused me a little)....
2.57 to 1 means you win 2.57 for every 1 time you loose

so it 2.57/(2.57+1) * 100 = 2.57/3.57 * 100 = 72%

starting from 72% means you win 72 out of 100 or you loose 100-72 =28
so its 72/28 which reduces down to 2.57 to 1
• Ok, then what is the example trying to show?:

/Users/roy/Desktop/Screen Shot 2016-09-26 at 12.43.26 PM.png
• sorry, reposting pic:
• Lets try this one more time: • Original example: • Wouldnt it just be easier here (above) to say we are 2.7:1 for instead?

It seems the 0.37 is calculated by dividing the remainder of of 100-73 (27) by the 73 and then putting this number :1.

Definitely confuses me. It seems simpler to say that anything above 50% equity would just be for as opposed to a dog.....

• Red Chipper Posts: 1,018 ✭✭✭✭
I think the confusion you may be having is that odds can be quoted in two ways....

3 to 1 or 4 for 1...these two are the same....

In the to format you get your original bet back and 3 more...by in the for format you don't get your original bet back.

If you ever looked at a crap table...some list the 66 (12) Payout as 30 for 1 while others list it at 29 to 1.....

Honestly when calculating poker I only look at the %...and compare it to the % I need....I never bother with odds....

Given the above example I would calculate the % total pot after I call 310....have to call 80, that about 27%.....have 32 outs (how we have 32 outs no idea but then I did not read the book assume 1 card to come) rule of 2 need 64% equityish....easy call...

If I was then pressed to calculate the odds....(because of the bonus you get when you do this right)...I would just use the 27%.. (100-27/27) or a bit less then 3 to 1..but if you prefer....100/27 for a bit less then 4 for 1.....
• Red Chipper, RCP Coach Posts: 278 ✭✭✭
edited September 2016
This thread has derailed into a ton of flawed math. All of you are confusing odds and probabilities. Percentages are probability (a number between 0 and 1). This will hopefully help:

http://www.quickanddirtytips.com/education/math/is-there-a-difference-between-odds-and-probability
• Thank you Matt,

I am comfortable with the content of the link that you posted. My question still remains though in regards to why @Doug Hull is presenting the equity of 73% (probability) as 0.37:1 (odds) vs simply stating 2.7:1 for.

I now understand how to come up these numbers in both ways but it seems counterintuitive to be thinking in these <1:1 numbers when dealing specifically with odds. I would think that as soon as a specific situation's equity is above the 50% probability threshold it is easier to start saying X:1 for instead of <1:1.

Should I comfortable with both?
• I convert it to a close familiar fraction. Here you have 8:1. Off the top of my head I didn't know what % that is. But I do know that 4:1 is the same thing as 25% and the odds for 8:1 is twice as worse as that, or 25%.

Not sure if that explanation makes sense. But this is what I did in my head: 4:1 is 25% so 8:1 is 12.5%
• Uh oh,

4:1 is not 25% but rather 3:1

Same with 8:1

Probably worth checking out the link that Matt posted above.
• edited September 2016
Touche. Misstatement on my part. of course I know that a 1 in 4 chance is a the same as a 25% chance while 4:1 against means you have a 20% chance of winning. In game I keep everything as ratios mostly.
• Red Chipper, RCP Coach Posts: 278 ✭✭✭
edited September 2016
Roy wrote: »
Thank you Matt,

I am comfortable with the content of the link that you posted. My question still remains though in regards to why @Doug Hull is presenting the equity of 73% (probability) as 0.37:1 (odds) vs simply stating 2.7:1 for.

I now understand how to come up these numbers in both ways but it seems counterintuitive to be thinking in these <1:1 numbers when dealing specifically with odds. I would think that as soon as a specific situation's equity is above the 50% probability threshold it is easier to start saying X:1 for instead of <1:1.

Should I comfortable with both?

Because bookmaker odds are read as x to 1 against. Since we are examining the case of the favorite we instead look at the inverse odds which are 27/73 = .3698 thus .37 to 1, or in other words we'd have to Lay 2.7 to 1 in order to give our opponent the correct price-- which is simply a conversion to the dog's price (1/.37 in simplified fractional form or 73/27). Are you following how this applies?
• Read it like a book. Thx a lot 