Calculating Geometric Growth

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Calculating Geometric Growth

EarthandAllStars

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December 18, 2007 at 8:12 pm

#119877

My math may be really rusty, but I don't understand how this formula works.
Future usage = current usage x (1 + growth rate)^{number of periods}
The examples given are:
Database size in 3 years = 600 x (1 + .02)³⁶
Database size in 3 years = 600(1.02)³⁶
Database size in 3 years = 600(2.04)
Database size in 3 years = 1224
I get the last part, but how does (1.02)³⁶ = (2.04) :ermm:

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Jason Selburg SSC-Insane Points: 24641 More actions · Answer 1

It's 1.02 to the 36th power or

1.02*1.02*1.02*1.02*1.02*1.02*1.02*1.02

*1.02*1.02*1.02*1.02*1.02*1.02*1.02*1.02

*1.02*1.02*1.02*1.02

=2.039887

Which in your example has been rounded up.

😀

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EarthandAllStars SSC Enthusiast Points: 178 More actions · Answer 2

Thanks! Now how do I do that on a regular calculator other than press the keys 36 times?

Jason Selburg SSC-Insane Points: 24641 More actions · Answer 3

*laughs*

I used Excel. 😎

______________________________________________________________________

Personal Motto: Why push the envelope when you can just open it?

If you follow the direction given HERE[/url] you'll likely increase the number and quality of responses you get to your question.

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Jeff Moden SSC Guru Points: 1003873 More actions · Answer 4

james.simonsen (12/18/2007)
Thanks! Now how do I do that on a regular calculator other than press the keys 36 times?

Ummm... Windows' calculator has a very nice scientific mode. And Jason is correct... spreadsheet would do fine. Or, you can do it in T-SQL...

PRINT POWER(1.02,36)

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
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karthik M One Orange Chip Points: 29139 More actions · Answer 5

what does the formula can do ? I am very confused.Can any experts explain me in detail ?

karthik

Jeff Moden SSC Guru Points: 1003873 More actions · Answer 6

This would be a very good place for you to lookup the POWER function in Books Online... it has a full explanation.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

colin.Leversuch-Roberts SSC Guru Points: 52643 More actions · Answer 7

I got someone to write me an excel spreadsheet which I just entered the figures and it worked it out for me!

In most cases database growth is pure guesswork unless you have long established trending.

[font="Comic Sans MS"]The GrumpyOldDBA[/font]
www.grumpyolddba.co.uk
http://sqlblogcasts.com/blogs/grumpyolddba/

karthik M One Orange Chip Points: 29139 More actions · Answer 8

Sorry,if my question confused you.I asked about the below formula.

My math may be really rusty, but I don't understand how this formula works.
Future usage = current usage x (1 + growth rate)number of periods
The examples given are:
Database size in 3 years = 600 x (1 + .02)36
Database size in 3 years = 600(1.02)36
Database size in 3 years = 600(2.04)
Database size in 3 years = 1224
I get the last part, but how does (1.02)36 = (2.04)

karthik

humbleDBA Hall of Fame Points: 3490 More actions · Answer 9

Hi karthikeyan,

What the formula is doing is compounding the percentage growth of 2% per month for 36 months.

So, if your database is 600 GB, then after the 1st month it will be 600*(1.02). For the 2nd month it will be 600*(1.02)^2, ie 600*(1.02*1.02). for the 3rd Month 600*(1.02)^3...and so it goes on. By the end you will have 600*(1.02)^36 -- which gives the 'estimated' growth you believe you will have (if you believe your database to grow at a rate of 2% per month for the next 36 months).

So, if you multiply 1.02 by the power of 36 [ie, (1.02*1.02*1.02*1.02...) 36 times], you will get the value 2.04 (or 2.03988734371570426901079658556 if you want to be more precise 😉 ). Therefore, based on your assumption of 2% growth per month for the next 36 months, your database at the end of the 36 months is likely to be 600*2.04 = 1,224 GB.

HTH

karthik M One Orange Chip Points: 29139 More actions · Answer 10

karthik M

One Orange Chip

Points: 29139

January 3, 2008 at 2:32 am

#764293

Thanks HumbleDBA.

karthik