How to estimate tag cost?

A few years ago, I found a site that was like an easy calculator...it estimated your tag cost based on your mileage in the states you were registered for. I *thought* I bookmarked the site, but I can't find it now. Tags are due at the end of the month and I am trying to figure out how hard our wallet is going to get hit. Anyone stumbled across an online calculator like this?

I guess the long way to go around would be to calculate miles and pro rate the tags myself, but I would like confirmation that is how they are figured.

Also, does anyone know if you estimate miles for a state, but don't travel in them, is there any credit factored in for the next years tags?

Finally, my husband usually registers for many states that he doesn't travel in because you never know where the road will take you, but if we cut back on the states, what exactly do you do to get a temp for a state you only need to go in once? How long does that take to obtain?

Thanks from MD!
Dawn

 

Okay answered my own first question. irponline.org under Information Exchange is the fee estimator. If you only knew how long I looked before finally breaking down and posting..only to find it right after LOL