Recipe formulation and IBU calculations

What IBU formula do you prefer when calculating your recipes: Tinseth, Rager, or Garetz?

Reason for asking is because I never see this listed on recipes and it could make a difference when calculating IBU's.

Does anyone feel this matters?

It probably matters more that you're consistent in what you use. Don't use Rager for one recipe and Tinseth for another. If you're consistent, your first few recipes will teach you how calculated IBUs relate to perceived bitterness and you can make adjustments if you don't like the finished product. If you keep changing formulas, tweaking recipes becomes harder.

That said, I've noticed significant differences in calculated IBUs when I've changed formulas from Tinseth to Rager. All else being equal, Rager seems to give significantly more IBUs when I play with the bitterness tool in Beersmith.

Right. When formulating my own recipes, I'll certainly stick to one as a standard.

I've noticed the differences as well. I think the default on Beersmith is Tinseth so most recipes I brewed in the past used that formula. However, I recently became concerned with reproducing recipes as closely as possible and began messing around with formulas. There can be quite a difference depending which you use!

This got me thinking that many of the recipes I've "re-created" in the past may have been off. I looked at the recipes and none of them have the IBU formula listed so there's no way of knowing what the brewer intended.
I know JZ uses Rager and when I make his recipes that's what I use. But if you use a different formula, the differences can be huge.

When using a recipe off of this database, for example, what do you assume the formula to be? Do you ask the brewer, or am I striving too hard for perfection?