What is this calculator for?
You're 38, you've contributed 6% to your 401(k) for the last 10 years, and your balance is $134,000. Your boss just announced the company is increasing the match from 4% to 5%, and you're wondering: if you bump your own contribution from 6% to 10% now, what does that mean for your retirement at 65? The 401(k) planner projects your retirement balance under various contribution and match scenarios, factoring in employer match, IRS contribution limits, and reasonable investment return assumptions.
2026 IRS contribution limits (annually inflation-indexed): $24,500 employee elective deferral. $8,000 catch-up contribution for age 50+. $77,500 total annual contribution limit (employee + employer + after-tax). Most workers contribute well below these limits β the median 401(k) balance for workers in their 50s is around $200K, vs the ~$1M+ needed for typical retirement. The plan: contribute enough to capture full employer match (the #1 priority β it's free money), then ramp up beyond match as income grows.
This calculator models compound growth over decades. Inputs: current balance, contribution rate, employer match formula, expected investment return (default 7% real), years until retirement. Output: projected balance at retirement plus year-by-year breakdown.
How to use this calculator
Enter your current age and target retirement age. Standard retirement assumption: 65. Early retirement (FIRE movement targets): 50-55. Working longer than 65 dramatically extends compounding time and reduces required savings rate.
Enter your current 401(k) balance, annual salary, and employee contribution rate (percent of salary). The IRS limit ($24,500 in 2026) caps absolute dollars; high earners hit the cap before reaching their percentage target. Catch-up contributions ($8,000 in 2026) become available at age 50.
Enter your employer match formula. Common formats: "50% match up to 6% of salary" (employer matches half of your contributions up to 6% of pay). "100% match up to 4%" (full dollar-for-dollar up to 4%). "Safe Harbor: 3% non-elective" (employer contributes 3% of your salary regardless of your contribution). Always contribute at least to the full match β anything less leaves money on the table.
Set your expected investment return. Default 7% nominal is reasonable for diversified stock-heavy portfolios over multi-decade horizons (historic S&P 500 has been ~10% nominal, 7% real after inflation). More conservative bond-heavy portfolios: 4-5% nominal. The calculator can model real or nominal; for retirement planning, real returns (inflation-adjusted) produce results in today's purchasing power.
Indicate salary growth rate: typical wage growth runs 2-3% nominal annually. Career advancement can add 5-10% in specific years.
Understanding your results
The calculator returns projected retirement balance at your target retirement age, year-by-year accumulation, total employee contributions, total employer match captured, and total investment growth.
How to read it. A 35-year-old earning $85K, contributing 10%, with 4% employer match, 7% real return, retiring at 65: projected balance $1.45M in today's dollars. Employee contributions: $310K. Employer match: $124K. Investment growth: $1.02M (70% of final balance is market growth, 30% is the contributions). The math is dramatic: $13,500/year of out-of-pocket contributions becomes a $1.45M balance over 30 years.
The employer-match-is-free-money insight. A 4% employer match on $85K salary = $3,400/year. Failing to capture full match (e.g., contributing only 2% and getting only $1,700 match) costs $1,700/year β over 30 years at 7% real, that's $172K of lost retirement balance. Match capture is the single most important 401(k) decision; the actual contribution rate beyond match is the secondary decision.
The contribution-rate decision. After capturing match, the relevant question is "how much more can I afford to contribute?" Common heuristics: 15% total of income (employee + employer combined) for typical retirement timeline. 20%+ for aggressive savers or those starting late. Use the calculator to find the contribution rate that produces an adequate retirement balance β typically $1-2M depending on lifestyle and other income sources (Social Security, pension, real estate).
The Roth-versus-traditional question. Traditional 401(k): contribute pre-tax (saves current tax), withdrawals taxed in retirement. Roth 401(k): contribute post-tax (no current tax savings), withdrawals tax-free in retirement. Decision factor: tax rate now vs in retirement. If your tax rate will be HIGHER in retirement (rare but possible for high-earning savers): Roth wins. If LOWER: traditional wins. Most workers' rates drop in retirement, so traditional wins; high earners increasingly do "Roth conversions" later in career to manage future RMD taxes. Many plans now allow split contributions (some traditional + some Roth) β common allocation is 70-80% traditional for high earners, 50/50 for middle earners.
A worked example
Lisa, 28, just landed a $72K job at a company offering "Safe Harbor 4% match + 50% match on next 2% of contributions." Translation: she gets 4% of $72K = $2,880 automatic if she contributes anything (or even nothing β Safe Harbor is non-elective), plus 1% additional ($720) if she contributes 2%. Total possible employer contribution: $3,600/year if she contributes at least 2%.
Scenario A: Lisa contributes 2% of salary ($1,440), captures full match ($3,600). Total annual: $5,040 going in. Salary growth 3%/year, return 7% real, retirement at 65. Projected balance at 65: $812K. Decent but tight for retirement living.
Scenario B: Lisa contributes 10% ($7,200), match still $3,600 (max). Total $10,800/year. Same growth assumptions. Projected balance at 65: $1.78M. Comfortable retirement on standard 4% withdrawal rate ($71K/year withdrawals).
Scenario C: Lisa starts at 10% and increases by 1% per year as salary grows, until she hits IRS cap. By age 40, contributing 18% of $108K = $19,440 (still under IRS cap). By age 50, at IRS cap + catch-up. Projected balance at 65: $2.7M.
Scenario D: same Lisa but waits until age 38 (just like 50% of US workers) to start contributing at 10%. Same career, same returns, just 10 years of delay. Projected balance at 65: $920K. Less than HALF of Scenario B despite same contribution rate, just because of 10 fewer years of compounding. The 10 years cost her ~$860K of final retirement balance.
The instructive comparison: A vs B differ only in employee contribution rate (2% vs 10%). The difference in retirement balance ($970K) is 5.6Γ the cumulative extra contributions ($5,760/year Γ 37 years = $213K). The 5.6Γ multiplier is what 37 years of compounding does to extra dollars contributed early in career. There is no path to building serious wealth that doesn't go through 'contribute early and consistently.'
Related resources
For underlying compound-growth math, see Compound Interest Calculator. For inflation-adjusted projection context, the Inflation Calculator. For Social Security projection that combines with 401(k) for total retirement income, the Social Security Estimator. For tax-advantaged healthcare savings, the HSA & FSA Maximizer. The IRS retirement plans page covers contribution limits, distribution rules, and the Saver's Credit available to lower-income retirement savers.