What is a 401(k) and how does it work?

A 401(k) is an employer-sponsored retirement savings plan defined under Section 401(k) of the Internal Revenue Code. Employees elect to have a percentage of their paycheck contributed directly to the account, either pre-tax (Traditional) or after-tax (Roth). Many employers match a portion of employee contributions, effectively providing free additional savings. The funds are invested in options chosen by the employee, typically including mutual funds, index funds, and target-date funds. Withdrawals before age 59.5 generally incur a 10% penalty plus income taxes, while qualified withdrawals in retirement are taxed according to the account type. For example, if you earn $80,000 and contribute 10% to a Traditional 401(k), your taxable income drops to $72,000, saving you approximately $1,760 in federal taxes at the 22% bracket.

How does employer matching work in a 401(k)?

Employer matching means your company contributes additional money to your 401(k) based on your own contributions. The most common formula is a 50% match on the first 6% of salary you contribute. For example, if you earn $60,000 and contribute 6% ($3,600), your employer adds $1,800 (50% of $3,600), for a total annual contribution of $5,400. According to the Bureau of Labor Statistics, the average employer match rate is between 3% and 6% of salary. Some employers use dollar-for-dollar matching up to a lower percentage, such as 100% match on the first 3%. Financial advisors universally recommend contributing at least enough to capture the full match, as it represents an immediate 50-100% return on your contribution before any investment gains.

What are the 2025 401(k) contribution limits?

For 2025, the IRS set the employee elective deferral limit at $23,500 for workers under age 50. Employees aged 50 and older can make an additional catch-up contribution of $7,500, bringing their total to $31,000. The combined employee-plus-employer contribution limit is $70,000 (or $77,500 with catch-up). Under the SECURE 2.0 Act, workers aged 60-63 receive an enhanced catch-up limit of $11,250 starting in 2025, bringing their total potential deferral to $34,750. These limits are adjusted annually for inflation by the IRS, and the 2026 limits are expected to be slightly higher.

What is the difference between a 401(k) and an IRA?

A 401(k) is employer-sponsored with higher contribution limits ($23,500 in 2025), while an IRA (Individual Retirement Account) is opened independently with a $7,000 annual limit ($8,000 if 50+). The 401(k) may include employer matching, which IRAs do not offer. IRAs typically provide a wider selection of investment options since you are not limited to your employer's plan menu. Many financial advisors recommend contributing enough to your 401(k) to get the full employer match first, then maxing out an IRA, then returning to max out the 401(k). Both account types are available in Traditional and Roth variants with similar tax treatment.

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

When you leave a job, you have four main options for your 401(k): roll it over to your new employer's plan, roll it into an IRA, leave it in your former employer's plan, or cash it out. Rolling over to an IRA is often the best choice because it gives you the widest investment selection and typically lower fees. Cashing out triggers a 10% early withdrawal penalty plus income taxes if you are under 59.5, which can consume 30-40% of your balance. For example, cashing out a $100,000 balance at age 35 in the 22% tax bracket would cost you $10,000 in penalties plus $22,000 in federal taxes, leaving only $68,000. Plus, you lose decades of compound growth on that money.

How much should I contribute to my 401(k)?

Most financial advisors recommend saving 10-15% of your gross income for retirement, including employer match. At minimum, contribute enough to capture the full employer match. According to Fidelity, the average 401(k) contribution rate in 2024 was 9.4% of salary, with total savings rates (including employer match) averaging 14.1%. If you are starting late or want to retire early, aim for 15-20%. Use this calculator to model different contribution percentages and see how each scenario affects your projected retirement balance. Even a 1% increase in contributions can add tens of thousands of dollars over a 30-year career.

401k Calculator – Estimate Your Retirement Balance

Quick Answer

A 401(k) is an employer-sponsored retirement account that lets you contribute pre-tax income, often with an employer match. The IRS 2025 employee contribution limit is $23,500 ($31,000 if age 50+). Projected balance = future value of all contributions plus employer match, compounded at the expected annual return.

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Current Age

Retirement Age

Current 401k Balance ($)

Annual Salary ($)

Your Contribution (%)

0% 10% 30%

Employer Match (%)

e.g. 50 = employer matches 50 cents per dollar

Employer Match Cap (% of salary)

Employer matches up to this % of your salary

Expected Return (% p.a.)

Projected Balance at Retirement

Total Employee Contributions

Total Employer Match

Total Investment Earnings

2025 Contribution Limits: $23,500 (under 50) | $31,000 (50+)

How a 401(k) Works

A 401(k) is an employer-sponsored defined-contribution retirement plan that allows employees to save and invest a portion of their paycheck before taxes are taken out. According to the IRS, 401(k) plans are the most common type of employer-sponsored retirement plan in the United States. As of 2024, approximately 70 million Americans actively participate in a 401(k), holding a combined $7.7 trillion in assets according to the Investment Company Institute.

This calculator projects how much your 401(k) could grow by the time you retire. It takes your current balance, annual salary, contribution percentage, employer matching formula, and expected investment return to model the growth trajectory year by year. The employer match is essentially free money added on top of your contributions, making it one of the highest-return financial decisions available to workers. Use this alongside our retirement calculator to see whether your total savings will support your desired retirement lifestyle.

The 401(k) Growth Formula

Your 401(k) balance grows through the future value of a series of regular contributions compounding over time. The formula used by this calculator is:

FV = PV(1 + r)ⁿ + PMT × [((1 + r)ⁿ − 1) / r]

Where:

FV = future value (projected balance at retirement)
PV = present value (current 401k balance)
r = monthly rate of return (annual return / 12)
n = total months until retirement
PMT = total monthly contribution (employee + employer match)

Worked example: A 30-year-old earning $75,000 with a $25,000 current balance contributes 10% ($7,500/year) and the employer matches 50% up to 6% of salary ($2,250/year). At a 7% annual return over 35 years to age 65, the projected balance is approximately $1,428,000. Of that, $262,500 came from the employee, $78,750 from the employer, and over $1 million from compound growth.

Key 401(k) Terms You Should Know

Vesting schedule: Determines when you fully own employer-matched contributions. A 3-year cliff vesting means you get 0% until year 3, then 100%. A 6-year graded schedule might vest 20% per year starting in year 2.
Employer match: The amount your employer contributes based on your own contributions. Common formulas include 50% match up to 6% of salary or dollar-for-dollar up to 3%.
Catch-up contributions: Additional contributions allowed for employees aged 50 and older, above the standard annual limit.
Required Minimum Distributions (RMDs): Mandatory withdrawals from Traditional 401(k)s that must begin at age 73 under the SECURE 2.0 Act. Roth 401(k)s are no longer subject to RMDs starting in 2024.
Early withdrawal penalty: A 10% tax penalty on distributions taken before age 59.5, in addition to regular income tax on Traditional 401(k) withdrawals.

Traditional 401(k) vs Roth 401(k)

The key difference between Traditional and Roth 401(k) contributions is when you pay taxes. Your choice has a significant long-term impact on your retirement income.

Feature	Traditional 401(k)	Roth 401(k)
Contributions	Pre-tax (reduces taxable income now)	After-tax (no current tax break)
Withdrawals	Taxed as ordinary income	Tax-free (if qualified)
RMDs	Required starting at age 73	Not required (since 2024)
Best for	Higher tax bracket now, lower in retirement	Lower bracket now, higher in retirement
2025 Contribution Limit	$23,500 ($31,000 if 50+)	$23,500 ($31,000 if 50+)

Practical 401(k) Examples

Example 1 -- Early career, aggressive saver: Maria, age 25, earns $55,000 and contributes 15% ($8,250/year). Her employer matches dollar-for-dollar up to 3% ($1,650/year). With a $0 starting balance and 8% average return, she accumulates approximately $2,390,000 by age 65. Her total contributions are $330,000; the remaining $2.06 million comes from employer match and compound growth.

Example 2 -- Mid-career catch-up: James, age 45, earns $100,000 and has $150,000 saved. He contributes 10% ($10,000/year) with a 50% match up to 6% ($3,000/year). At 7% returns, he reaches approximately $860,000 by age 65. If he increases contributions to 15% and maxes out catch-up contributions starting at 50, the total rises to roughly $1,050,000.

Example 3 -- Late start, maximum effort: Sarah, age 55, earns $120,000 with $200,000 saved. She contributes the maximum $31,000 (including catch-up) with a 50% match up to 6% ($3,600/year). At 6% returns over 10 years, she reaches approximately $720,000. Starting late limits compounding time, but maximizing contributions and match still adds meaningful growth.

Tips to Maximize Your 401(k)

Always capture the full employer match: Not contributing enough to get the full match is leaving free money on the table. If your employer matches 50% up to 6%, contribute at least 6%.
Increase contributions with every raise: When you get a 3% raise, increase your 401(k) contribution by 1-2%. You will never miss money you did not see in your paycheck.
Choose low-cost index funds: According to Vanguard, a 1% difference in expense ratios can reduce your balance by over 25% over 30 years. Target-date funds and S&P 500 index funds typically have expense ratios below 0.10%.
Consider Roth contributions if you are early in your career: Lower-income years are the best time to pay taxes upfront through Roth contributions, as your future tax rate is likely to be higher.
Avoid early withdrawals: A $50,000 withdrawal at age 35 costs you the $50,000 plus a $5,000 penalty plus income taxes, and you lose decades of compounding on that money -- potentially $300,000+ by retirement.
Review and rebalance annually: Ensure your asset allocation still matches your risk tolerance and time horizon. Most plans offer automatic rebalancing features.

2025-2026 401(k) Contribution Limits

The IRS announced the following limits for 2025 tax year. For 2026, the employee limit is expected to increase to $24,000 based on cost-of-living adjustments, though the official announcement is pending.

Limit Type	2025	2024
Employee contribution (under 50)	$23,500	$23,000
Catch-up contribution (50+)	$7,500	$7,500
Total employee + employer limit	$70,000	$69,000
Total with catch-up (50+)	$77,500	$76,500

Disclaimer: This calculator is for informational purposes only and does not constitute financial, tax, or legal advice. Always consult a qualified professional for decisions specific to your situation.

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