Savings Goal Calculator
"How long to save $1 million?" or "How much do I need to contribute per month?" Compare the answer across a Roth IRA, Traditional 401(k), and taxable brokerage account — all framed as after-tax spendable value.
The amount you want to be able to spend, net of withdrawal tax.
Post-tax contributions, tax-free growth and qualified withdrawals
Pre-tax contributions, tax-deferred growth, taxed at withdrawal
Post-tax contributions, dividends taxed annually, capital gains on sale
Comparisons are framed in after-tax value — what you can actually spend after withdrawal tax — so a 401(k) doesn't look artificially bigger than a Roth just because contributions are pre-tax.
Roth IRA: tax-free qualified withdrawals. Traditional 401(k): growth is tax-deferred, but withdrawals taxed at your marginal rate. Taxable brokerage:approximated with annual tax drag at your marginal rate (a conservative upper bound — long-term capital gains and dividend-qualified rates will usually do better).
The goal is checked at year-end. Actual time-to-goal is at most 11 months later than shown (mid-year → year-end granularity).
Frequently asked questions
How long will it take to save $1 million?
At 7% annual return with no starting balance, you need about $650/month for 40 years, $1,075/month for 30 years, or $1,920/month for 25 years — to reach $1 million in a tax-free Roth IRA. Timeline in a taxable brokerage account is longer because of annual tax drag on dividends and realized gains; in a Traditional 401(k) the gross number gets there faster, but after-tax withdrawal tax reduces what you can actually spend. This calculator shows all three on the same after-tax basis.
What is a realistic rate of return to use?
Historically, a diversified US stock portfolio has returned about 7% real (after inflation, before tax). A 60/40 stock/bond portfolio has returned closer to 5-6% real. Entering 7% is standard for long-term planning, but check whether the goal is in today's dollars (use the real return) or nominal future dollars (use a nominal return like 9-10% and expect the goal to be bigger in future terms).
Why does the calculator compare accounts on an after-tax basis?
A Traditional 401(k) balance of $1 million isn't the same as a Roth IRA balance of $1 million — the 401(k) still owes income tax at withdrawal. If your marginal rate is 24%, that $1M in a 401(k) is only $760,000 of real spending power. Framing goals in after-tax terms makes the comparison apples-to-apples and matches how you should actually plan for retirement spending.
What if my goal isn't reachable even at high monthly contributions?
If the result shows 'Not reachable' or '> 80 years', the goal is too large for the horizon and return you've entered. Options: extend the horizon, raise the expected return (within reason — 10% real is aggressive), lower the goal, or contribute more aggressively early to leverage compounding.
How does the monthly required amount differ across wrappers?
For the same after-tax goal: Roth IRA requires the lowest monthly contribution (tax-free withdrawals). Taxable brokerage requires more (annual tax drag compounds into a larger gap). Traditional 401(k) sits in between — you need more contributions (in pre-tax dollars) because a share of the withdrawal will be taxed, but pre-tax contributions reduce the current-year tax bite, which isn't reflected in the monthly number shown. If your current and retirement tax rates are identical, Roth and 401(k) converge; if retirement rate is lower, 401(k) wins.
Sources
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