Quote from dima777:
After checking this formula I corrected it to:
=CEILING(LOG(1-B1,(100-A1)/100),1)
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My formula posted (which is equivalent to MTE's later post btw) shows how many trades to get to the remaining balance as a percentage
of original capital. i.e. 30% of original capital, where CL=30%
ntrades = ln(CL)/[ln(1-lt)]
ntrades = number of trades to get to CL
CL = Cumulative loss
lt = loss/trade
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I was thrown off a bit by some of the earlier posts; particularly when you use 50% which gives the same answer in both instances.
What you really wanted was 1-CL, or the amount you would have to lose to get to some percentage of the original capital.
simply change formula to:
ntrades = ln(1-CL)/[ln(1-lt)]
where the variable, lt, is the absolute value of loss each trade.
you'll get the same results as the formula
(can use the ceiling function to round up as well) you posted, which in simple math says:
logyx=n (excel's argument reverses the terms)
here y is base :
where x = 1-CL
y = (100-lt)/100
or alternatively,
(1-lt/100)^n = 1 - CL
the only other difference is you have it so B1 (1-CL) is entered as a raw value reflecting a percentage, yet A1 is entered as the value that is converted to the raw percentage value. Both of my variables are entered directly as raw values reflecting the percentage.
i.e.
=CEILING(LOG(1-F11,1-F10),1)
=CEILING(LN(1-F11)/(LN(1-F10)),1)
should both give same,
where
Fll = final percentage of original principle
F10 = percentage loss per trade
ex :
F10 = loss/trade = 1/100
F11 = final percentage of principle = 30/100
both return 36.
Cheers