401(k) Calculator

How the 401(k) Calculator Works

A 401(k) calculator projects your retirement account balance by combining three growth engines: your own contributions, your employer's matching contributions, and compound investment returns. The core formula is a future value of annuity calculation: FV = PV × (1+r)^n + PMT × [((1+r)^n - 1) / r], where PV is your current balance, r is the monthly return rate, n is months to retirement, and PMT is total monthly contributions (yours plus employer match).

For example, a 35-year-old with a $50,000 current balance, contributing 10% of an $85,000 salary with a 4% employer match and 30 years to retire at a 7% annual return, would accumulate roughly $1.2 million by retirement. The employer match alone contributes over $140,000 in that scenario — free money that doubles your effective contribution rate.

401(k) Contribution Limits for 2025

The IRS sets annual contribution limits that change periodically. For 2025:

• Employee contribution limit: $23,500 (up from $23,000 in 2024)
• Age 50+ catch-up contribution: Additional $7,500 → maximum $31,000
• Age 60–63 super catch-up (SECURE 2.0): Additional $11,250 instead of $7,500, starting 2025
• Total combined limit (employee + employer): $70,000 for 2025

Always contribute at least enough to capture your full employer match — this is a 50–100% instant return on your money. If your employer matches 50% up to 6%, contributing only 3% means leaving 3% of your salary in forfeit every year. On a $70,000 salary: $2,100/year in lost free money.

How Much Should I Have in My 401(k) by Age?

Fidelity's widely-cited savings benchmarks:

• By age 30: 1× your annual salary saved
• By age 35: 2× your salary
• By age 40: 3× your salary
• By age 50: 6× your salary
• By age 60: 8× your salary
• By age 67: 10× your salary

On a $80,000 salary: target $80,000 by 30, $240,000 by 40, $480,000 by 50, $800,000 by 67. These are targets, not rules. Starting at 40 instead of 25 makes it harder, but consistently maxing contributions for 25 years can still produce a comfortable retirement — the math still works, it just requires more savings rate.

The Power of Time: Why Starting Early Changes Everything

Consider two identical employees both earning $70,000, contributing 10% with 4% employer match at 7% annual return:

• Sarah starts at 25, retires at 65: 40 years → approximately $2.3 million
• Michael starts at 35, retires at 65: 30 years → approximately $1.1 million
• Difference: $1.2 million more from starting 10 years earlier, despite only $98,000 in additional contributions ($9,800/year × 10 years)

The extra $98,000 in contributions produces $1.2 million in additional wealth. That's not a misprint — compounding over decades transforms modest early contributions into enormous amounts. Each decade of delay roughly cuts your final balance in half.

Understanding Your Results

The calculator breaks your projected balance into four components:

• Balance at Retirement: Total projected value including all growth
• Your Contributions: The actual dollars you've put in over the years
• Employer Match Total: What your employer contributed on your behalf
• Investment Growth: The compounding returns on top of all contributions

For most people who start contributing in their 20s or 30s, investment growth ends up being the largest component — often exceeding the combined total of personal and employer contributions. A 30-year investor in a 7% return environment sees roughly 70% of their final balance come from investment growth, not from dollars they personally contributed.

401(k) vs. Roth 401(k): Which Is Better?

Traditional 401(k) contributions are pre-tax, reducing your taxable income now and deferring taxes until withdrawal. Roth 401(k) contributions are after-tax, meaning withdrawals in retirement are completely tax-free.

• Traditional 401(k): Best if you're in a high tax bracket now and expect lower bracket in retirement (common for peak earners in 40s–50s)
• Roth 401(k): Best if you're early career in a low bracket, or if you expect tax rates to rise in the future
• Split strategy: Many advisors recommend contributing to both for "tax diversification" — hedging against unknown future tax rates

What Return Rate Should You Use?

The S&P 500 has averaged roughly 10% annually before inflation over the past century. A diversified portfolio including bonds typically returns 6–8% over long periods. Guidelines by risk profile:

• Age-appropriate target date fund (most common): Use 7% for 20–30 year horizons
• Aggressive (mostly stocks): 8–9% long-term assumption
• Moderate (60/40 stocks/bonds): 6–7% long-term assumption
• Conservative (mostly bonds): 4–5% long-term assumption

Don't use rates above 10% — they create unrealistic expectations. Don't use rates below 4% unless you're near retirement and genuinely in a conservative allocation. The return rate is the single most sensitive input in the calculation — the difference between 6% and 8% over 30 years roughly doubles your final balance.

Frequently Asked Questions

What happens to my 401(k) if I change jobs?

You have four options: leave it with your former employer (acceptable if they have good investment options), roll it into your new employer's 401(k) (consolidates accounts), roll it into an IRA (most investment flexibility, typically lowest fees), or cash it out (expensive — you'll owe income tax plus 10% early withdrawal penalty if under 591/2). Rolling into an IRA is usually the best choice for investment options and fee minimization.

Can I withdraw from my 401(k) early?

Yes, but expensively. Withdrawals before age 591/2 incur regular income tax plus a 10% penalty. On a $20,000 withdrawal in the 22% bracket: about $6,400 lost to taxes and penalties — plus you permanently forfeit the compound growth that money would have earned. SECURE 2.0 added new penalty-free exceptions for domestic abuse victims, terminally ill, and disaster victims. Loans from 401(k) are an option but risky if you leave your job.

What's a typical employer 401(k) match?

Most common: 50% match on the first 6% of salary (you contribute 6%, they add 3% = total 9%). Some employers offer dollar-for-dollar up to 3–4%. Average employer match across U.S. companies: about 4.3% of employee salary, per Vanguard's 2024 plan report. Always read your benefits documentation to understand your exact formula — matching structures vary widely.

What is vesting and how does it affect my 401(k)?

Vesting determines when you fully own the employer match. Common schedules: immediate vesting (you own all employer contributions from day one — increasingly common), 3-year cliff vesting (0% until year 3, then 100%), and graded vesting (20% per year over 5 years). If you leave before fully vested, you forfeit unvested employer contributions. Always consider vesting status before accepting a new job or leaving — unvested employer contributions can represent thousands of dollars of foregone compensation.