Enter your salary, contribution rate, and employer match to see exactly how much your 401(k) will grow by retirement — including the power of compounding over decades.
A 401(k) is a tax-advantaged retirement savings account offered through employers. Contributions are made from pre-tax income, which lowers your taxable income today. The money grows tax-deferred — meaning you don't pay taxes on gains, dividends, or interest until you withdraw in retirement. Most financial experts consider the 401(k) the single most powerful savings tool available to working Americans.
For 2025, you can contribute up to $23,500 per year to a 401(k), or $31,000 if you're 50 or older (catch-up contributions). Many employers match a portion of contributions — typically 50 cents to a dollar for every dollar you contribute, up to 3–6% of your salary. That match is effectively a 50–100% instant return on your contribution, which makes capturing the full match the highest-priority financial move for most workers.
Traditional 401(k) contributions are pre-tax: you get a tax break now and pay income tax on withdrawals in retirement. Roth 401(k) contributions are after-tax: you pay taxes now, but withdrawals in retirement are completely tax-free, including all growth. If you expect to be in a higher tax bracket in retirement — or if you're early in your career with decades of compounding ahead — a Roth 401(k) often wins. If you're in your peak earning years and want to reduce your current tax bill, traditional is often the better choice.
Time is the most powerful variable in retirement savings. Contributing $500/month starting at 25 with a 7% return produces roughly $1.3 million by 65. Starting the same contributions at 35 produces only about $610,000 — less than half, for only ten fewer years of contributions. This is the compounding effect: growth builds on prior growth. Every year you delay costs significantly more than the contributions themselves.
The U.S. stock market has historically returned about 10% annually before inflation, or roughly 7% after inflation. A diversified 401(k) invested in low-cost index funds is a reasonable proxy for that return over long periods. More conservative portfolios (with more bonds) will return less but fluctuate less. Most financial planners use 6–7% as a realistic long-term assumption for diversified portfolios. Use a conservative estimate if you're within 10–15 years of retirement.
You can start withdrawing from a 401(k) without penalty at age 59½. Early withdrawals before that age trigger a 10% penalty plus income tax on the amount withdrawn — a significant cost. Required Minimum Distributions (RMDs) must begin at age 73. If you leave a job, you can roll your 401(k) into an IRA or your new employer's plan without taxes or penalties. Leaving money in an old 401(k) is usually suboptimal because of limited investment options and higher fees compared to a self-directed IRA.
A common benchmark is saving 15% of your gross income for retirement, including any employer match. If you started late, 20% or more may be necessary to catch up. At minimum, always contribute enough to capture your full employer match — not doing so is leaving guaranteed compensation on the table. Use this calculator to find your specific number based on your age, income, and retirement goals.