This is an online tool offered by Dave Ramsey (crosses self, throws salt over shoulder). There is a free version (yay!) and a pay version (boo!) that links to your bank account. Apparently the pay version automatically uploads your banking transactions and dumps them into the categories. I'm going to go out on a limb and assume that you cannot link to credit cards, since in the Dave Ramsey universe they are from Satan. So if you use two or three credit cards for rewards purposes (which I do), the pay version would not be all that helpful anyway. If you don't use credit cards and you don't want to manually log in your transactions, and you really want to pay a monthly fee to Dave Ramsey, knock yourself out.
In any event, the free version is super easy to use, and you can customize the categories and sub-categories however you like. The basic concept of the zero based budget is that you assign every dollar from your income to an expense category. How it works out in practice is you dump any residual into savings. Obviously you can start with gross income if you want to so that you can see the percentages that come out for taxes, insurance, retirement contributions, or whatever. Because those numbers are the same every month and I already know what they are, I find it much more useful just to start with net take home income, and allocate money that flows through the checking accounts. If you are a newbie at this and you are using credit cards (for rewards purposes), please note that the credit card payments are not an expense! Your purchases on the cards are an expense, so that is what you log. The payment you make to pay off your credit card in full every month is really treated as an internal transfer.
I went backwards in time and did a six month historical analysis and the results were interesting. I don't think I will track forever, but if you have never done this I guarantee you will find a few leaks you weren't aware of, or you will find some areas that you want to reallocate.
The link is:
www.everydollar.com