I currently have a rollover IRA which I no longer contribute to and a 401k which I currently contribute to. I would like a Roth account to be more diversified from a tax perspective. I currently put 12% into the 401k (the company matches 0.5% on the first 6%, so I get an addition 3% of company match). I would like to reduce my 401k contribution to 6% and put the remaining 6% into the Roth IRA.

My questions are, how do I make sure that I am contributing an equal amount? It's not completely clear what 6% of pretaxed income equals in post tax amount. And, is going from 12% pretaxed/0% Roth to 6% pretax/6% Roth too much Roth or how do I determine if I have a sufficient spread of pretax and Roth savings?


  • 2
    Did you check that you're allowed to contribute to Roth from income limit perspective?
    – littleadv
    Commented Jul 1, 2015 at 15:39
  • 1
    Does the company offer a Roth 401(k)? Commented Jul 1, 2015 at 18:18

1 Answer 1


The exact answer will come from looking at the "taxable income" line on your tax return. You take that number and see what marginal rate this puts you at.

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Say you are single (you didn't specify). After deductions, exemptions, etc, these are the rates for taxable income. If you are at $38,000, the last dollars were taxed at 25%, so it would take $1000 pretax to net $750 to deposit to Roth.

If you offer some specific numbers we can give you an answer for your exact situation.

There's no perfect solution, just understanding the choice you face each year, and adjusting it as the numbers change.

I know your question was just regarding how to calculate the net deposit to Roth, but there's a larger discussion of how to make the decision between the two accounts, and whether 50/50 should be the goal.)

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