Min/Max 401k Comparison
Maximum Versus Minimum 401k Contribution Comparison
This online calculator is meant to compare different allocations for a 401k and Roth IRA.
This page will show you what could happen if you currently contribute some amount to a 401k and you want to reduce your contributions to the 401k and increase contributions to a Roth IRA by that amount.
Instructions
 Enter information into the greenshaded section below (item 1, 2, 3, and 4)
 Click the Compare button
 You may view the intermediate results (no shading) or you may ignore them
 The end results are in the yellowshaded section (items 18 and 19)
Explanations for Each Step

How much money one earns a year
In this example, this figure is used for determining how much is contributed to a 401k fund per year.

How many years one will be contributing to the 401k
In this example, this figure is used for determining how many annual contributions will occur and how much compounding will take place.

What percent of one’s salary one deducts before taxes for a 401k
In this example, this figure is used for determining how much is contributed to a 401k fund per year.
The first category is what one currently contributes or would like to contribute, in percent of salary. This is an interactive example so you could try various situations.
The second category is the minimum amount, in percent, of what one needs to contribute in order to get the full company matching amount. 
How well one’s fund performs
In this example, this figure is used for determining how much compounding will take place.
The 401k rate is under the Max column and the IRA rate is under the Min column.
Any calculations, whether for the Min column or the Max column, will use the 401k rate for the 401k and the IRA rate for the IRA. 
What annual dollar amount one contributes to a 401k
In this example, this figure is used for determining how much is added to the 401k fund each year.
This is calculated by taking a percentage (item 3) of the annual salary (item 1).

What annual dollar amount one contributes to a Roth IRA
In this example, this figure is used for determining how much is added to the IRA fund each year.
This is calculated by taking a percentage (item 3, max minus min) of the annual salary (item 1).

One’s pay after 401k but before taxes
In this example, this figure is used for determining how much income is to be taxed.
This is calculated by subtracting the 401k contributions (item 5) from the annual salary (item 1).

How much one is taxed (percent)
In this example, this figure is used for determining how much income is to be taxed.
This is calculated by comparing pretrax salary (item 7) to the federal tax tables.

How much one is taxed (dollars)
In this example, this figure is used for determining how much tax to subtract from one’s pay.
This is calculated by taking a percentage (item 8) of the pretrax salary (item 7).

How one’s taxes add
In this example, this figure is used for determining how much tax one has paid over the years.
This is calculated by multiplying the annual tax amount (item 9) by the number of years (item 2).

How one’s taxes compound
In this example, this figure is simply for fun.
This is calculated by compounding the annual tax amount (item 9) over the number of years (item 2).

What one takes home after 401k contributions and taxes
In this example, this figure is used for determining the difference used in the next step.
This is calculated by the annual tax amount (item 9) and 401k contributions (item 5) from the annual salary (item 1).

How much more one takes home
In this example, this figure is used for determining how much more one could contribute to a Roth IRA in the Max case.
This is how much more one takes home (in the max 401k case as opposed to the min 401k case) because of the increased pretax salary deductions.
This is calculated by the two values of takehome pay (item 12, max case – min case). The value with more pretax deductions (max 401k) will be larger since the taxes will be lower.

How much more one takes home, compounded
In this example, this figure is used for determining how much more one could have in a Roth IRA in the Max case.
This is calculated by compounding the annual takehomepay difference (item 13) over the number of years (item 2).

How much one has at the moment he retires
In this example, this figure is used to show how much one would have at retirement, before taxes.
This is calculated by compounding the annual 410k contributions (item 5) and IRA contributions (item 6) over the number of years until retirement (item 2).

How much one pays in taxes on that retirement amount
In this example, this figure is used to adjust the retirement amount to reflect reality.
This is calculated by taking a percentage (item 3) of the retirement amount (item 15).

How much one has at retirement
In this example, this figure is used to show how much one would have at retirement, after taxes but without the takehome pay difference.
This is calculated by subtracting the retirement taxes (item 16) from the retirement pretax total after compounding (item 15).

How much one really has at retirement
In this example, this figure is used to show the net effect (end result) of various 401k and IRA allotments.
This is calculated by adding the retirement total (item 17) to the extra IRA contributions from the extra takehome pay (item 14).

How much one has paid in taxes
In this example, this figure is used to show what the government will have received at the time of retirement.
This is calculated by adding the total annual taxes paid (item 10) to the retirement taxes paid (item 16).