# Reverse Engineering A Fold Equity Calculator

moldyfish
Red Chipper Posts:

**99**✭✭
Hey y'all,

Question: Can someone show me the equation which RCP's fold equity calculator uses to solve?

https://redchippoker.com/fold-equity-calculator/

example: we are on the river. pot is $100. villain bets half-pot (50). I raise 3.5x the bet (175). I have 18% equity.

Inputs for FE calc:

Pot Before Shove (P): 150

How Much to Call (B): 50

How Much is Shove (R): 175

Equity (E): 18%

Output:

Fold Equity (F): 39%

How can I reverse engineer this? I am looking to use it in an google spreadsheet.

If you could, please use the variables above and solve for F. Thank you.

Question: Can someone show me the equation which RCP's fold equity calculator uses to solve?

https://redchippoker.com/fold-equity-calculator/

example: we are on the river. pot is $100. villain bets half-pot (50). I raise 3.5x the bet (175). I have 18% equity.

Inputs for FE calc:

Pot Before Shove (P): 150

How Much to Call (B): 50

How Much is Shove (R): 175

Equity (E): 18%

Output:

Fold Equity (F): 39%

How can I reverse engineer this? I am looking to use it in an google spreadsheet.

If you could, please use the variables above and solve for F. Thank you.

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## Comments

317✭✭✭Anyway, I believe it's using something like this:

0 = [(P + B) * F] + (1 - F)*[(P + R)*E - R*(1 - E)]

So, equilibrium is when

The money we make when he folds PLUS

The money we make when he calls and loses MINUS

The money we lose when he calls and wins

Equals 0.

Then, just rearrange the equation to solve for F.

99✭✭this is unclear.

and yes i am aware of that equation, not the rearranging.

4,249-I seem to recall doing this once and producing a quadratic.

317✭✭✭I'm pretty sure the pot and any bets you are facing are left as separate variables, because you may or may not be facing a bet and this would be an elegant way to separate the two numbers.

4,249-That's correct, I think. By including any bet you're facing it allows a calculation of your raise size from your bet. Not the only way to set it up, but a relatively clean one.

1,018✭✭✭✭When called your equity is %equity * final pot - your bet(not including the call)

we will call this E (equity in final pot)

when they fold we win the pot...or P

so is the fold equity is X then the times they call is (1-x)

The amount we win when they fold has to equal the amount we loose when they call)

xp = (1-x)e

xp = e-xe

xp +xe = e

x(p+e) = e

x = e/(p+e)

In a spread sheet I would calculate final pot, and E and then use it in this final formula.

1,876-It was confusing as anything to implement because the plug-in we use was meant for "Sum these two numbers" and rather simple things like that. I do not remember the exact formula used, but I derived it from published sources and "I are an enginer" so the math is right. You will need to re-derive as has been done above.

Author Poker Plays You Can Use

Author Poker Workbook for Math Geeks

99✭✭I was attempting to figure it out to build this interactive fold equity calculator.

The formula for which was

=(-Q2*(((3.5*A6)/(1+A6))+(1)+((3.5*A6-A6)/(1+A6)))+((3.5*A6)/(1+A6)))/(-Q2*(((3.5*A6)/(1+A6))+(1)+((3.5*A6-A6)/(1+A6)))+((3.5*A6)/(1+A6))+(1))

Where Q2 is equity and A6 is the percentage of pot of the initial bet.

@Roblivion and @TheGameKat , i’m fairly certain you are not correct about how to input the fold equity calculator. The pot at the decision point is the initial pot + bet. It matches up in my table.

317✭✭✭You're absolutely right. When I drop the equity to 0 and I change the amount you have to call, it doesn't change the FE calculated at all, which means it's not changing the size of the total pot based on the amount bet. It must only be using that to back into the amount V would have to call to calculate what you would win in cases when you win.