There are several websites out there with a fiscal cliff calculator, but the one 23 ABC came across seems to be the most simple.
The website is BankRate.com.
On that site, there is a link that will figure out how going over the fiscal cliff will affect your income.
All you have you to do is put in three pieces of information: household gross income, how many exemptions you have and your filing status.
Hit 'calculate' and then you can see the tax bill under current law and compare it to what it would be over the fiscal cliff.
The direct link: http://www.bankrate.com/calculators/tax-planning/fiscal-cliff-calculator/