Re: How to calculate development time?

[arhuman]

I use the following rules when I try to estimate developping time :

• No serious estimation without complete specs
• Don't assume that when you do several times the same thing you'll do it faster
  (In fact you'll probably get bored and it will balance the speed gained by experience)
• No real task should be made professionnaly in less than half a day
  (Real analysis,Test, Documentation...Not only implementation)
• Try to estimate the time to do each small task, sum up, then multiply by 2
  (test, client interaction, integration...)
• If I don't have total control I can't produce correct estimation
  (state it but try to give an estimation anyway :
  "Provided the ISP had mod_perl properly configured it will take X hours, add X hours if I have to only use PHP...")
• Any addition to the specs will change the estimation
  (even if they take something out, beccause your prior analysis and possibly data structure may be now inadequate...)

Following those guidelines have saved me several time.
"Only Bad Coders Code Badly In Perl" (OBC2BIP)

[clemburg]

Try to estimate the time to do each small task, sum up, then multiply by 2 (test, client interaction, integration...)

You can get better at that factor. Keep a backlog of your estimates and the actual time you actually needed. This way, you can adjust the multiplication factor for future estimates. The factor will vary with many influences, including working environment, project scope, growing experience, business domain, quality requirements, and so on ad infinitum. Still, you will get much better estimates by recording your past performance, and extrapolating from that by way of an adjusted multiplication factor.

Christian Lemburg
Brainbench MVP for Perl
http://www.brainbench.com

[arhuman]

You're obviously right...

I just wanted to emphazize that whatever the time you estimate,
increase it to be able to handle all the possible problems which may arise.
(Furthermore I've whitnessed that almost everybody tend to be too optimistic when estimating...)

You won't lost a penny if you are thru before the deadline.
But being late is always VERY unpleasant.

"Only Bad Coders Code Badly In Perl" (OBC2BIP)