401(k) Calculator 2026 | Retirement Savings, Employer Match & ROTH Scenarios

This US 401(k) calculator models your retirement savings by combining several core inputs: your current 401(k) balance (if any), your annual salary in US dollars, the percentage of pay you contribute, your employer's match formula, expected investment return, projected salary growth, and the number of years until retirement. For each year between your current age and retirement age, the engine:

- Estimates your salary for that year based on the salary growth rate you choose. - Applies your employee contribution rate to that salary, subject to projected IRS-style elective deferral and total contribution limits. - Calculates your employer's matching contribution using the match rate and match limit you provide, again constrained by a conservative total 401(k) limit. - Adds employee and employer contributions to your opening balance, then applies your expected annual rate of return to grow the account for that year.

By repeating this process for every year until retirement, the calculator produces a year-by-year projection of your 401(k) balance, total contributions, and investment growth. You can also specify a state income tax rate to approximate the combined impact of US federal and state taxes on your Traditional 401(k) withdrawals versus Roth-style after-tax savings.

Under the hood, this US 401(k) calculator uses standard time-value-of-money and compounding formulas that financial planners apply every day. At a high level, the ending balance for each year is:

Ending balance = (Opening balance + Total contributions) × (1 + r_net)

where r_net = Annual return % − Expense ratio %. This means plan fees are deducted from the gross return each and every year — which is how real-world mutual fund and ETF fees work inside 401(k) plans.

Employee contributions are calculated as:

Employee contribution = Min(Salary × Contribution %, 2026 IRS employee deferral limit + applicable catch-up)

For 2026, the elective deferral limit is $23,500. Under SECURE 2.0, if you are aged 50–59 or 64+, you may contribute an additional $7,500 catch-up. If you are aged 60–63, you qualify for the enhanced "super catch-up" of $11,250.

Employer contributions are based on your employer match structure, for example "100% match on the first 4% of pay":

Employer contribution (before caps) = Salary × Min(Match %, Match limit %)

Then the calculator enforces the 2026 IRS annual additions limit of $70,000 so that:

Employee contribution + Employer contribution ≤ $70,000.

To estimate after-tax values for Traditional versus Roth 401(k), the model approximates an effective federal income tax rate using simplified 2026 US tax brackets and adds your selected state income tax rate. It applies a modestly lower effective tax rate at retirement, reflecting that many households have lower taxable income in retirement than during peak earning years. Roth-style balances are treated as after-tax and are not reduced again in the projection, assuming IRS rules for qualified withdrawals are met.

Retirement income is estimated using the 4% Sustainable Withdrawal Rate (SWR), dividing projected after-tax balance by 25 and showing the monthly equivalent. This widely used rule of thumb — first described by William Bengen in 1994 — suggests a 30-year portfolio historically supported a 4% annual withdrawal with a high probability of not being depleted. It is a planning estimate, not a guarantee.

Consider a 30-year-old worker in the United States earning $75,000 per year, with an existing 401(k) balance of $25,000. They contribute 8% of pay to the plan, their employer matches 50% of contributions up to 4% of salary, they expect a 7% average annual return before inflation, long-run US inflation of 2.5%, and modest salary growth of 2.5% per year. They plan to retire at age 65.

1. In year one, salary is $75,000. The employee contributes 8% of pay, or $6,000. The employer match is 50% of the first 4% of pay (4% of $75,000 is $3,000), so the employer adds $1,500. Total contributions for the first year are $7,500, subject to IRS-style annual caps, which this calculator enforces conservatively. 2. The opening balance of $25,000 plus $7,500 of contributions grows at 7%, leading to an end-of-year balance of approximately $34,225. 3. In year two and beyond, salary increases by 2.5% annually, so contributions rise with pay. Each year, the engine re-applies the same contribution formulas and growth rate, producing a detailed amortization-style schedule of balances, contributions, and growth. 4. By age 65, this worker could see a projected 401(k) balance well into seven figures in nominal dollars. The inflation-adjusted balance in today's dollars is lower, but more meaningful for planning retirement lifestyle and US living costs.

The calculator also estimates a Traditional after-tax value by applying an effective tax rate at retirement, and a Roth after-tax value that reflects taxes paid upfront rather than at withdrawal. The summary section highlights the difference between these two approaches so users can see how much tax timing may matter over a multi-decade horizon.

A powerful way to use this US 401(k) calculator is to compare at least two scenarios side by side. For example:

Scenario A – Aggressive contributions: You contribute 10% of a $75,000 salary, receive a 4% employer match, expect a 7% annual return, and allow your contribution percentage to increase by 1% per year until you reach the IRS limit. Scenario B – Conservative contributions, conservative portfolio: You contribute 5% of salary, still receive the 4% match, but assume a 5% annual return and no automatic contribution increases.

Over a 30–35 year career, Scenario A will usually produce a substantially higher projected 401(k) balance because both the contribution rate and the compounding engine are doing more work. However, Scenario B may feel more comfortable for someone prioritizing short-term cash flow or investing in a lower-volatility mix of US stocks and bonds.

By adjusting the "Expected Annual Return", "Annual Salary Growth", and "Annual Contribution Increase" fields and rerunning the calculator, you can explore how different assumptions interact. For many US households, steadily raising contribution rates over time often has more impact on retirement readiness than small tweaks to investment return assumptions.

Several recurring 401(k) mistakes show up clearly when you experiment with the inputs in this calculator:

- Not contributing enough to secure the full employer match, which effectively leaves guaranteed compensation unused. - Keeping contribution rates flat for years even as salary climbs, leading to retirement savings that lag behind lifestyle inflation and higher US living costs. - Using unrealistically high return assumptions that underestimate risk and volatility in US and global markets. - Ignoring the impact of inflation, resulting in a retirement balance that looks large in dollars but has far less purchasing power in the future. - Failing to consider tax diversification between Traditional (pre-tax) and Roth (after-tax) 401(k) options, which can make retirement withdrawals less flexible.

When you adjust the inputs to remove these mistakes – for example, by increasing contributions to at least the match threshold, turning on modest contribution step-ups, and using a realistic return range – the projected 401(k) path often changes meaningfully.

This US-focused 401(k) calculator is most useful for workers who participate in an employer-sponsored 401(k) plan and want a structured way to test contribution strategies. It is particularly valuable when:

- You are starting a new job in the United States and need to decide how much of your paycheck to defer into the 401(k). - Your employer changes its match policy and you want to see how the new formula affects long-term retirement savings. - You receive a raise, bonus, or promotion and are deciding how much extra to direct toward retirement versus near-term goals. - You are evaluating Traditional versus Roth 401(k) contributions and want a directional view of after-tax outcomes. - You are within 10–15 years of retirement in the US and want to stress-test whether current savings rates and investment assumptions are on track.

For comprehensive retirement planning, pair this calculator with tools that model Social Security benefits, IRA or Roth IRA contributions, and required minimum distributions (RMDs) to capture the full picture of US retirement income.