How This Calculator Works
A 401(k) projection compounds five cash flows: your starting balance, ongoing employee contributions, employer match, investment returns, and salary growth. The model advances year by year so contributions can grow with raises.
End Balance = (Start Balance + Employee Contribution + Employer Match) × (1 + r)
Where:
- Employee Contribution = min(Salary × Contribution%, IRS Limit)
- Employer Match = min(Employee Contribution, Salary × Match Limit%) × Match%
- r = expected annual return
The employer match is the most valuable part. A typical plan matches 50% of contributions up to 6% of salary — meaning if you earn $80,000 and contribute 6% ($4,800), the employer adds $2,400. That is an immediate 50% return on your contribution. Failing to capture the full match is the worst financial mistake a 401(k) participant can make.
2024 Limits: Employee $23,000 | Catch-up (50+) $7,500 | Total $69,000
The model caps employee contributions at the IRS limit. Employer matches, profit-sharing, and non-elective contributions count toward the much higher $69,000 total limit. Older workers can add $7,500 in catch-up contributions (this calculator does not model age-based catch-ups automatically — add them to your contribution rate manually).
Doubling time ≈ 72 ÷ annual return (%)
At 7% returns, your 401(k) balance doubles roughly every 10 years. A 30-year-old with $50,000 saved who never contributes another dollar still reaches about $380,000 by age 65. The same 30-year-old contributing $10,000/year reaches about $1.4 million — but only $350,000 of that comes from contributions; the other $1.05 million is investment growth. Important caveats: 401(k) balances are tax-deferred, not tax-free. Withdrawals in retirement are taxed as ordinary income (federal plus state). Required Minimum Distributions (RMDs) begin at age 73 (as of SECURE Act 2.0). Roth 401(k) contributions, increasingly common, offer tax-free growth but use after-tax dollars. Auto-escalation features, now common in 401(k) plans, automatically increase your contribution rate by 1% per year until you hit a cap (often 10%–15%); research from Vanguard shows this adds tens of thousands of dollars to retirement balances with minimal perceived pain.
When to Use This Calculator
Use the 401(k) calculator when you want to:
- Decide how much to contribute — does bumping from 5% to 10% meaningfully change the outcome?
- Quantify the value of your employer match and how much you would lose by not capturing it
- Compare a job offer with a better 401(k) match versus one with a higher salary
- Model the impact of a salary increase, bonus, or raise on retirement readiness
- Decide whether to make Roth or traditional 401(k) contributions
- Plan catch-up contributions after age 50 to close a retirement savings gap
- Stress-test different return assumptions (conservative 5% vs historical 8%–10%)
- Decide whether to enable auto-escalation, which gradually increases your contribution rate each year
Re-run the calculation annually and after major life events — marriage, job change, or inheritance. Many plans also offer automatic escalation; enabling it can quietly add six figures to your retirement balance over a 30-year career. The 401(k) match is a key component of total compensation that many workers fail to evaluate when comparing job offers.
Example Calculation
A 35-year-old earns $80,000/year, has $40,000 already in a 401(k), contributes 8% of salary, and expects 7% annual returns with 3% salary growth. The employer matches 50% of contributions up to 6% of salary. She plans to retire at 65.
Year 1 math:
- Employee contribution: $80,000 × 8% = $6,400 (well under the $23,000 limit)
- Matchable contribution: min($6,400, $80,000 × 6% = $4,800) = $4,800
- Employer match: $4,800 × 50% = $2,400
- Total contribution year 1: $6,400 + $2,400 = $8,800
- End-of-year balance: ($40,000 + $8,800) × 1.07 = $52,216
Over 30 years (with salary and contributions growing 3%/year):
- Total employee contributions: about $304,000
- Total employer match: about $114,000 (free money)
- Projected balance at 65: about $970,000
- Total investment growth: about $552,000
Notice the employer match contributes $114,000 directly, but compounding turns that into roughly $300,000 of the final balance. Not capturing the match would cost about $300,000 in retirement wealth — a devastating loss for what is essentially free money. If she increases contributions to 15% (capturing the full match plus extra), her projected balance jumps to about $1.55 million. Bumping contributions by even 1% per year via auto-escalation typically adds $100,000+ to the final balance.
If she changes jobs and her new employer offers no match, her projected balance drops by roughly $300,000 — a powerful argument for negotiating 401(k) match as part of any job offer. Conversely, if her new employer matches dollar-for-dollar up to 5% (instead of 50% up to 6%), her total employer contribution nearly doubles, adding about $200,000 to her final balance. The 401(k) match is a key component of total compensation that many workers fail to evaluate when comparing job offers — a $5,000/year match difference compounded over 30 years is worth far more than a $5,000 salary difference.