I wrote a spreadsheet (<< it may not be obvious - this is a link to pull down the spreadsheet) a while back that might help you. You can start by putting your current salary next to your age, adjust the percent of income saved (14% for you) and put in the current total.
The sheet basically shows that if one saves 15% from day one of working and averages an 8% return, they are on track to save over 20X their final income, and at the 4% withdrawal rate, will replace 80% of their income. (Remember, if they save 15% and at retirement the 7.65% FICA /medicare goes away, so it's 100% of what they had anyway.)
For what it's worth, a 10% average return drops what you need to save down to 9%. I say to a young person - try to start at 15%. Better that when you're 40, you realize you're well ahead of schedule and can relax a bit, than to assume that 8-9% is enough to save and find you need a large increase to catch up.
To answer specifically here - there are those who concluded that 4% is a safe withdrawal rate, so by targeting 20X your final income as retirement savings, you'll be able to retire well.
A 2014 update - retirement spending needs are not the same for everyone. When I cite an 80% replacement rate, it's a guess, a rule of thumb that many point out is flawed. The 'real' number is your true spending need, which of course can be far higher or lower. The younger investor is going to have a far tougher time guessing this number than someone a decade away from retiring. The 80% is just a target to get started, it should shift to the real number in your 40s or 50s as that number becomes clear.
Next, I see my original answer didn't address Social Security benefits. The benefit isn't linear, a lower wage earner can see a benefit of as much as 50% of what they earned each year while a very high earner would see far less as the benefit has a maximum. A $90k earner will see 30% or less. The social security site does a great job of giving you your projected benefit, nd you can adjust target savings accordingly.