(Taking you seriously) Try keeping a log of your estimations and the actual time taken. Write down both the original two day estimate and the extended 11 day one.
Then after a few months you should have a good set to look at and hopefully convince yourself to believe your modified estimates. Or how to adjust your formula to be more accurate.
Comments
Here's mine:
Double it, add another unit up. So, two days becomes four days + 1 week = 11 days. I've found this (depressingly) accurate over a large sample size.
The only problem is, for each new task, I refuse to accept that such a "ridiculous" estimation could be correct, so I just stick with the original.
And the cycle continues...
(Taking you seriously) Try keeping a log of your estimations and the actual time taken. Write down both the original two day estimate and the extended 11 day one.
Then after a few months you should have a good set to look at and hopefully convince yourself to believe your modified estimates. Or how to adjust your formula to be more accurate.
(agreeing), I believe that's called velocity. This skill will help any programmers while doing consulting.