401(k) Calculator
Estimates your 401(k) balance at retirement by compounding your employee contributions and employer match monthly at your expected return (7% a year if left blank). Ideal for evaluating how much of your salary to contribute and whether you're capturing your full employer match.
Last updated: September 2026
Formula below · 3 sources (IRS, dol.gov, Wikipedia) · Updated Sep 2026
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About this calculator
A 401(k) grows through three forces: your own pre-tax contributions, your employer's matching contributions, and compound investment returns. Each month, your employee contribution equals annualSalary × contributionPercent / 100 ÷ 12, capped at the 2026 IRS deferral limit of $24,500 a year, and the employer adds employeeContribution × (employerMatch / 100) — the match field is the percentage of your contribution the employer adds, so enter the rate that applies to the amount you actually contribute. The combined monthly deposit earns a monthly rate of the expected annual return ÷ 12 (0.07 / 12 ≈ 0.5833% at the 7% default). Salary raises and catch-up contributions are not modeled. The balance is updated each month as: balance = balance × (1 + monthlyRate) + monthlyTotal. After all months, this iterative formula produces the final balance. Employer matching is essentially a 50–100% instant return on your contribution, making it one of the highest-value benefits available to employees. Maximizing the match before directing money elsewhere is a fundamental personal finance principle.
How to use
Assume a $70,000 salary, 6% contribution, 50% employer match, and 30 years to retirement. Monthly employee contribution = ($70,000 / 12) × 0.06 = $350. Monthly employer match = $350 × 0.50 = $175. Monthly total = $525. Monthly rate = 0.07 / 12 = 0.005833. Over 360 months the iterative compounding yields: balance = $525 × ((1.005833^360 − 1) / 0.005833) ≈ $525 × 1,219.97 ≈ $640,485. Enter your real salary and match rate to see your projected balance.
Frequently asked questions
How much should I contribute to my 401(k) to maximize my employer match?
You should contribute at least enough to capture 100% of your employer's match, since unmatched dollars are effectively leaving free compensation on the table. For example, if your employer matches 50% of contributions up to 6% of salary, you need to contribute at least 6% to get the full match. Beyond that threshold, contributions still grow tax-deferred, but the instant return from matching no longer applies. Most financial planners recommend maxing the match first, then funding a Roth IRA, and finally returning to the 401(k) up to the IRS annual limit.
What is a realistic annual return rate to use for 401(k) projections?
This calculator uses the return you enter, or 7% per year if you leave it blank. 7% is roughly the S&P 500's long-run real (after-inflation) return; nominal returns have historically been closer to 10%, so 7% is a conservative and widely used planning assumption. Your actual return depends on your fund choices, expense ratios, and market conditions. Using a slightly lower rate (5–6%) gives a more conservative estimate if you hold a significant bond allocation.
What is the difference between a 401(k) and a Roth 401(k) for retirement savings?
A traditional 401(k) is funded with pre-tax dollars, reducing your taxable income today, but withdrawals in retirement are taxed as ordinary income. A Roth 401(k) is funded with after-tax dollars, meaning contributions don't reduce your current tax bill, but qualified withdrawals in retirement are completely tax-free. The better choice depends on whether you expect your tax rate to be higher now or in retirement. Younger workers in lower tax brackets often benefit more from the Roth option, while high earners near peak income typically prefer the traditional pre-tax deferral.