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Roth versus traditional 401k calculator

This calculator estimates how much you’ll gain/lose by contributing to your 401k pre-tax (traditional) versus after-tax (Roth). For simplicity, this calculator considers your contribution this year only (first input below), and assumes you’ll withdraw that entire amount in N years (last input below).

For the traditional option, this calculator assumes you invest this year's tax savings (in a taxable brokerage account) for the duration of the N years without trading (you only pay long-term capital gains taxes on this amount upon withdrawal).

Contribution amount (this year) [$]

Current marginal tax rate (annual) [%]

Interest rate earned on 401k savings (annual) [%]

Marginal tax rate in retirement (annual) [%]

Long-term gain tax rate in retirement (annual) [%]

Number of years until retirement withdrawl

You'll have $9321.80 extra in retirement with the Roth 401k.

  • The traditional 401k will save you $3600.00 this year which, if invested will grow to $24654.51 in 25 years.
  • After paying capital gains, the above savings amount to $21496.33.
  • However, your contribution of $15000.00 will grow to $102727.13 in 25 years.
  • The Roth option dodges $30818.14 in taxes upon withdrawal of the latter amount.