 Current age
 Your current age.
 Annual contribution
 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 2013 is $17,500. If you are age 50 or over, a "catchup" provision allows you to contribute even more to your 401(k). 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 "catchup" 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 $115,000 or more in 2013 or was $115,000 or more in 2012, you may need to contact your employer to see if these additional contribution limits apply to you.
 Expected rate of return
 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 types of investments you select. The S&P 500 for the 10 years ending Dec. 31st, 2012 had an annual compounded rate of return of 7.1%, including reinvestment of dividends. From January 1970 through the end of 2012, 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 12month return was 61% (June 1982 through June 1983). The lowest 12month return was 43% (March 2008 to March 2009). Savings accounts at a bank may pay as little as 0.25% 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 longterm 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 of retirement
 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.
 Current tax rate
 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.
10% 
$0  17,400 
$0  8,700 
$0  $12,400 
$0  8,700 
15% 
$17,400  70,700 
$8,700  35,350 
$12,400  47,350 
$8,700  35,350 
25% 
$70,700  142,700 
$35,350  85,650 
$47,350  122,300 
$35,350  71,350 
28% 
$142,700  217,450 
$85,650  178,650 
$122,300  198,050 
$71,350  108,725 
33% 
$217,450  388,350 
$178,650  388,350 
$198,050  388,350 
$108,725  194,175 
35% 
over $388,350 
over $388,350 
over $388,350 
over $194,175 
Source: Revenue Procedure 201152 http://www.irs.gov
 Retirement tax rate
 The marginal tax rate you expect to pay on your investments at retirement.
 After tax total at retirement
 For the Roth 401(k), this is the total value of the account. For the Traditional 401(k), this is the sum of two parts: 1) The value of the account after you pay income taxes on all earnings and tax deductible contributions and 2) what you would have earned if you had invested (in an ordinary taxable account) any income tax savings.
