401(k) Calculator

What is a 401(k)?

A 401(k) is an employer-sponsored retirement savings plan that allows you to invest a portion of your paycheck before taxes are taken out. Named after a section of the U.S. Internal Revenue Code, it is one of the most powerful wealth-building tools available to American workers. Your contributions grow tax-deferred — meaning you pay no taxes on the gains until you withdraw the money in retirement, typically after age 59½. Many employers also offer a matching contribution, effectively giving you free money on top of your own savings.

How can a 401(k) calculator help you?

Retirement planning without numbers is just guesswork. A 401(k) calculator shows you exactly how your contributions, employer match, salary growth, and investment returns combine over time to build your nest egg. By adjusting variables like contribution percentage, expected return rate, and retirement age, you can see the real cost of delaying savings — and the powerful impact of even small increases in your contribution rate. Use it to set concrete savings goals aligned with your retirement lifestyle.

How does the 401(k) growth formula work?

The 401(k) balance grows through the future value of a series of contributions (annuity), compounded annually. The core formula used is:

How to use Finzony's 401(k) calculator

Getting your retirement projection takes less than a minute. Follow these steps:

1. Enter your current age and retirement age: The gap between these two numbers is how long compound growth has to work for you.
2. Set your annual salary: This is the base for calculating your contribution amount and employer match.
3. Choose your contribution rate: Enter the percentage of your salary you contribute each pay period. At minimum, match what your employer will match.
4. Add your employer match details: Input your employer's match percentage and the salary cap it applies to (e.g., 50% match on up to 6% of salary).
5. Set expected annual return: Use 6–8% for a diversified portfolio. Be conservative — it's better to be pleasantly surprised.
6. Get your projection: The calculator instantly shows your estimated 401(k) balance at retirement, broken down year by year.

Advantages of a 401(k)

• Tax-Deferred Growth: Your investments grow without being taxed each year. You only pay taxes when you withdraw in retirement, allowing compound growth to work at full power.
• Employer Match = Free Money: Many employers match a portion of your contributions. Contributing at least enough to get the full match is an instant 50–100% return on that money.
• Reduces Taxable Income Now: Traditional 401(k) contributions are pre-tax, lowering your taxable income today. Contributing $10,000 could save $2,200+ in taxes if you're in the 22% bracket.
• Automatic & Disciplined Saving: Contributions are deducted from your paycheck automatically. You never see the money, so you're less tempted to spend it — making saving effortless.

Common 401(k) Mistakes to Avoid

• 1. Not contributing enough to get the full employer matchLeaving free money on the table is the single most common 401(k) mistake. If your employer matches 50% up to 6% of salary and you only contribute 3%, you're giving up thousands per year in free money — always contribute at least enough to capture the full match.
• 2. Cashing out when changing jobsCashing out your 401(k) instead of rolling it over triggers income tax plus a 10% early withdrawal penalty if you're under 59½ — potentially losing 30-40% of your balance instantly, on top of losing decades of future compound growth.
• 3. Being too conservative too earlyYounger workers with decades until retirement often keep too much in low-return conservative funds out of fear of market swings. Time in the market smooths out volatility — a heavier stock allocation when you're young typically leads to a much larger balance at retirement.
• 4. Not increasing contributions as salary growsIt's easy to set a contribution rate once and forget it. Bumping your contribution percentage by 1% each time you get a raise barely affects your take-home pay but compounds into a meaningfully larger retirement balance over time.

The Bottom Line

A 401(k) is one of the most powerful tools available for building long-term wealth, largely because of two things you can't easily replicate elsewhere: employer matching and tax-deferred compound growth. Use this calculator to find a contribution rate that captures your full match and puts you on track for the retirement you want, then revisit your numbers whenever your salary or goals change. Small, consistent increases in your contribution rate — especially early in your career — tend to matter more than chasing the perfect rate of return.