Your current age.

The amount you will contribute to a 401(k) each year. This calculator assumes that you make 12 equal contributions throughout the year at the beginning of each month. The annual maximum for 2010 remains at $16,500. If you are age 50 or over, a "catch-up" provision allows you to contribute even more to your 401(k). In 2010, employees age 50 or over can deposit an additional $5,500 into their 401(k) account. It is also important to note that employer contributions do not affect an employee's maximum annual contribution limit. Both the annual maximum and "catch-up" provisions are indexed for inflation.

It is important to note that some employees are subject to another form of contribution limits. Employees classified as "Highly Compensated" may be subject to contribution limits based on their employer's overall 401(k) participation. If you expect your salary to be $110,000 or more in 2010 or was $110,000 or more in 2009, you may need to contact your employer to see if these additional contribution limits apply to you.

The annual rate of return for your 401(k) account. This calculator assumes that your return is compounded annually and your deposits are made monthly. The actual rate of return is largely dependent on the type of investments you select. For example, from December 1999 to December 2009, the average annual compounded rate of return for the S&P 500 was -0.6%, including reinvestment of dividends. From January 1970 to December 2009, the average annual compounded rate of return for the S&P 500, including reinvestment of dividends, was approximately 10.1% (source: www.standardandpoors.com). Since 1970, the highest 12-month return was 61% (June 1982 through June 1983). The lowest 12-month return was -43% (March 2008 to March 2009). Savings accounts at a bank may pay as little as 1% or less but carry significantly lower risk of loss of principal balances.

It is important to remember that these scenarios are hypothetical and that future rates of return can't be predicted with certainty and that investments that pay higher rates of return are generally subject to higher risk and volatility. The actual rate of return on investments can vary widely over time, especially for long-term investments. This includes the potential loss of principal on your investment. It is not possible to invest directly in an index and the compounded rate of return noted above does not reflect sales charges and other fees that funds and/or investment companies may charge.

Age you wish to retire. This calculator assumes that the year you retire, you do not make any contributions to your 401(k). So if you retire at age 65, your last contribution happened when you were actually 64.

The current marginal income tax rate you expect to pay on your taxable investments. Use the table below to assist you in determining your current tax rate.

Source: http://www.irs.gov/pub/irs-drop/rp-09-50.pdf

The marginal tax rate you expect to pay on your investments at retirement.