401k contribution limits ($23k + $7.5k catch-up), matching formulas (dollar-for-dollar, partial, vesting), and compound growth projections from age 30 to 65.
The IRS sets annual contribution limits for 401k plans. For 2026, the employee elective deferral limit is $23,500, up from $23,000 in 2025. Participants aged 50 or older can make an additional catch-up contribution of $7,500, bringing the total to $30,000. The total combined limit (employee + employer contributions) is the lesser of 100% of compensation or $69,000 for 2026 ($76,500 with catch-up).
Employer matching is the most powerful feature of a 401k because it is free money. The most common matching formula is 50% of employee contributions up to 6% of salary. For an employee earning $60,000 who contributes 6% ($3,600), the employer adds 50% of that ($1,800), bringing the total annual contribution to $5,400. The employer match is also tax-deferred and grows tax-free until withdrawal.
| Match Formula | Employee Contributes | Employer Adds | Total Annual |
|---|---|---|---|
| 50% up to 6% | 6% ($3,600 on $60k) | $1,800 | $5,400 |
| 100% up to 3% | 3% ($1,800 on $60k) | $1,800 | $3,600 |
| 100% up to 4% | 4% ($2,400 on $60k) | $2,400 | $4,800 |
| 50% up to 10% | 10% ($6,000 on $60k) | $3,000 | $9,000 |
The growth of a 401k over time is driven by three factors: the contribution amount, the employer match, and the annual rate of return. The S&P 500 has returned approximately 10% annually on average over the long term (1926-2025, per Ibbotson/SBBI), though 7% is a more conservative planning figure that accounts for inflation and the fact that most 401k plans include bonds.
Consider a 30-year-old earning $60,000 who contributes 6% ($3,600/year) and receives a 50% match up to 6% ($1,800/year), for a total of $5,400/year. Assuming a 3% annual salary increase and a 7% annual return, by age 65 the 401k balance would be approximately $1,050,000. Of that, roughly $350,000 came from contributions and $700,000 from growth — the compound growth accounts for two-thirds of the final balance. With 10% annual returns, the same scenario reaches approximately $1,800,000.
The most important 401k rule is to contribute at least enough to get the full employer match. Failing to do so is leaving a guaranteed 50-100% instant return on your money. The Employee Benefit Research Institute (EBRI) estimates that roughly 20% of eligible employees do not contribute enough to capture the full match, effectively walking away from thousands of dollars per year in free compensation.
After securing the full match, the next priority is to increase your contribution rate over time. The general recommendation is to save 10-15% of your income (including the match) for retirement. If your plan offers a Roth 401k option, contributions are after-tax but qualified withdrawals are tax-free, which provides tax diversification in retirement. The Metriova 401k calculator models your account growth with your specific salary, contribution rate, match formula, and expected return, showing you the projected balance at any retirement age.
401k Growth Calculator — Employer Match Included
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