This maybe isn't for FIRE calculating, but I think it's the most helpful tool: mint.com
Once you know exactly how much you are saving and spending, all you have to do is divide the two, find your savings rate, and then check out the 'shockingly simply math' mmm blog post.
I'm sure other people will give you the correct calculators for calculating your fire date, but without mint.com (or some kind of tracking) you won't be able to use the calculators.