How do I ... Calculate my 401(k) savings at a given age?

What you need to know

Because of the unpredictable nature of investment returns and unforeseen fluctuations in income (layoffs, promotions), predicting 401(k) balances is an inexact science.

The good news is that with a few easy-to-obtain pieces of information, you can get a general idea of where you'll be 10, 20 or 30 years from now.

The first thing you'll need is your 401(k) balance. You can find this by looking at your 401(k) statement. By law, this must be sent to you at least once a quarter. Your 401(k) provider may provide online access. If so, you find your current balance there.

Then, estimate the rate of return you expect to get on your investments. This figure will depend largely on the aggressiveness of your portfolio. Stocks historically return about 10 percent a year over time, while bonds return about 5 percent. So, depending on the mix in your account, you'll probably come out somewhere in between.

Finally, look at what percentage of your income is going into your 401(k). Don't forget to include the employer match, which is often a 50 percent match up to a certain percentage of your salary. The amount your employer contributes should be recorded in your 401(k) statement.