Percentage change date calculation from initial value

I find that I must first figure these kinds of problems out mathematically before I can program them into the spreadsheet. Along those lines, how are you defining per cent change? Usually I expect something like (This value - Initial value)/Initial value, but that does not seem to coincide with any of your sample values. I expect that, if you will explain to us in mathematical terms how you calculate per cent change, we will be able to help you put that into Excel.

So, it is not the usual definition of per cent change that I am used to. If I follow your description correctly, it looks like y=A0*2^x where x is the per cent change. So:

100% -> 500*2^1=1000
200% -> 500*2^2=2000
-100% -> 500*2^-1 = 250
-200% -> 500*2^-2=125
50% -> 500*2^.5 = 500*1.4=707
-50% -> 500*2^-.5=500/1.4=354

and so on. Does that look right?

Assuming that is correct, if we are given y and A0 and need to solve for x, we will go back to our algebra lessons from long ago: http://www.purplemath.com/modules/solvexpo.htm

y=A0*2^x --> take the log of both sides
ln(y)=ln(A0)+x*ln(2) and so on until you solve for x. Then you can use that formula in your spreadsheet (pay attention to absolute and relative references) to compute the desired per cent change.

If the first / initial value is 500 then it is changed to +100 i.e., 1000 then for next value calculation i.e., next +100 % is 2000

For the better understandings the below values will help.

500 (Initial value)
1001 +100%
750
500 -100%
800
1200 +100%
1500
1800
2100
2450 +100%
2700
3800
4900 +100%
3200
2400 -100%
2000
1500
1100 -100%
700
500 -100%

As one who is a proponent of using helper columns, you are talking to the wrong guy asking for help to remove the helper columns. It looks like what you have works just fine, so I would tend to leave it as is. If you don't like to look at columns E:G, then you can hide them. Beyond that, I think someone else will have to step in and suggest some single cell megaformula that will eliminate the need for the helper columns.

Hi.

Just to clarify, then: your expected results are in column G? And you want to arrive at those results using the data in columns A and B but without using any helper columns, correct?

Regards