401(k) Calculator

How to Use the 401(k) Calculator

1. Enter your current age and expected retirement age.
2. Input your current 401(k) balance (check your plan statement).
3. Set your monthly contribution amount.
4. Enter your employer match — both the match percentage and the cap.
5. Use a 7% expected return as a moderate baseline (historical S&P 500 average, inflation-adjusted).

How a 401(k) Works

A 401(k) is an employer-sponsored retirement savings plan that lets you contribute pre-tax dollars from each paycheck. These contributions grow tax-deferred until withdrawal — meaning you don't pay taxes on earnings until you withdraw in retirement.

The employer match is one of the most valuable benefits in personal finance. When your employer matches 50 cents for every dollar you contribute up to 6% of salary, that's an immediate 50% return before any investment gains.

Over decades, the combination of regular contributions, employer matching, and compound growth transforms modest monthly savings into substantial retirement wealth. A 30-year-old contributing $500/month with a $250/month employer match at 7% will have approximately $1.3 million at age 65.

The 401(k) Growth Formula

Your 401(k) grows using future value of an annuity calculations for both your contributions and employer match, applied monthly:

Where PV is current balance, r is monthly return rate, n is months to retirement, and C is combined monthly contributions (yours + employer match). The employer match is calculated as: min(your contribution, salary × match_cap%) × match_rate%.

Real 401(k) Growth Examples

Example 1: Getting the Full Match

Lisa earns $70,000 and contributes 6% ($350/month). Her employer matches 100% up to 4% ($233/month). At 7%, starting at 32 with $15,000 balance, Lisa has $983,000 at 65.

Example 2: Maxing Out

David maxes his 401(k) at $23,500/year ($1,958/month) plus $700 employer match at 7%. Starting at 35 with $50,000, he accumulates $3.1 million by 65.

Example 3: Late Starter

Melissa starts at 45 with $0, contributes $800/month with $400/month employer match at 7%. She reaches $518,000 by 65 — still meaningful but shows the cost of starting late.

Tips to Maximize Your 401(k)

• Always capture the full employer match — it's a 50–100% immediate return.
• Increase contributions by 1% per year — small increases compound dramatically.
• Use target-date funds if you don't want to manage allocations — they auto-rebalance as you age.
• Avoid 401(k) loans — borrowed money loses compound growth while it's out of your account.
• Contribute to both Traditional and Roth if your plan offers both — diversify your tax exposure.
• Review your allocations annually — don't set and forget for decades.