due dates - another questions

[macha10]

I have a lot of questions today - sorry!

I am confused about due dates...big surprise. It's sort of hypothetical, because the different ways to calculate don't result in very different dates. And my midwife isn't going to argue with me over dates....
But I am still baffled by this.

I calculated my due date by both Naegele's rule (I believe this is the standard way, based on LMP) and the EDD is Jan 25, 2011. And I calculated by Prem rule - EDD is Jan 27th. But when I use online due date calculators they all come up with somewhere between Jan 22-Jan 23. Any idea why this happens? Don't they use the Naegele's rule?

Also why am I getting myself worked up into a tizzy about this????

[MaerynPearl]

Do you have 28 day cycles with 14 day lps?

if not, or you do not know... Naegele's rule is no good for you.

Granted, according to research its no good anyway because it gives you a due date that is too early.

[Jaimee]

If you makes you feel better, I was definitely in a tizzy about my due date with my first baby. It was very important to me to know exactly what week I was in at all times. A lot of this had to do with my intense morning sickness and me needing to have some sort of end point in mind. If I was 9 weeks vs 10 weeks, that was making a big difference to me!

I realized along the way that there is a lot of discrepancy regarding due dates and if you decide to have a 20 week sono, they will give you yet another due date. And FWIW, it seems to me that different sites, books, OB's, MW's, etc. all look at due dates a little differently, even the little wheels they use are a little different from brand to brand. In the end what is the most important IMO is to have the latest due date possible so that if you should go late, you have a cushion of time before they talk induction.