Tradition says "Two Months' Salary."
Cruel? Exorbitant? Extortion? Maybe, but this is the industry standard. Actually, there is a method to this madness. The thought is that if the guy can save up two month’s salary, at least there’s some basic stability in his life, as opposed to an 18-year-old with $97 bucks to his name. Some people say one month, some say three, some say it shouldn’t matter… but this is your safest route. By the way, a lot of sites have “widgets” to help you calculate the amount you to spend if you follow this rule of thumb. Hint: two months out of twelve is 16.66666666%. You don't need a widget. And you might be wondering…is that pre-tax or post-tax? Does it include your annual bonus? Before or after you account for 401(k) withholdings? All fair questions, but they all sort of miss the boat. The two months' salary adage is just to get you in the ballpark. No one will grill you on the exact dollars or percents. That said, pretax, and if your bonus is relatively guaranteed, yep, I’d throw it in the calculation.