What is the 401(k) Calculator?
A 401(k) calculator is a retirement projection tool that translates your current 401(k) balance, salary, contribution percent, employer match formula, expected annual return, and years to retirement into a single future value. It also breaks the result into the three components that drive it: your own contributions, the employer's matched dollars, and compounded investment growth. The point is to make the trade-offs visible so you can pick a contribution rate that hits your target without leaving free employer money on the table.
The 401(k) is the dominant US workplace retirement vehicle, named after Internal Revenue Code section 401(k). In 2026 the IRS lets you defer up to $23,500 of salary into the plan, with a $7,500 catch-up if you are 50 to 59 or 64 plus and an $11,250 SECURE 2.0 super catch-up if you are 60 to 63. Combined with the typical employer match (50 cents on the dollar up to 6 percent of salary is the modal formula), most US workers can fund a comfortable retirement entirely inside a 401(k) without ever touching an IRA or taxable brokerage account.
How the calculator works
The model iterates year by year. In each year it adds your contribution (capped at the IRS deferral limit) plus the employer match (the smaller of your contribution percent or the match cap, multiplied by the match rate), then grows the running balance by the annual return. Salary grows at the rate you enter, and the IRS limit is assumed to grow about 1 percent per year (the post-2025 indexation pattern).
FV = balance_0 x (1+r)^n
+ sum over each year y in [1..n]:
min(salary_y x pct, IRS_limit_y) x (1+r)^(n-y) # your dollars
+ salary_y x min(pct, match_cap) x match_rate
x (1+r)^(n-y) # employer match
- balance_0: your current 401(k) balance (vested plus unvested).
- salary_y: gross salary in year y, growing at your input rate.
- pct: percent of salary you defer (capped at IRS dollar limit).
- match_rate: employer's match rate (50 percent in the standard 50 on 6 formula).
- match_cap: the salary percent at which the match stops.
- r: annual return (nominal). Subtract inflation for a "today's dollars" view.
- IRS_limit_y: the 2026 base of $23,500 grown 1 percent per year as a planning assumption.
Worked example
Sarah is 35, earns $100,000, and contributes 10 percent of salary. Her employer matches 50 percent on the first 6 percent of pay. She expects a 7 percent nominal return and plans to retire in 30 years. Her starting balance is $25,000.
- Year one employee contribution: $100,000 x 10 percent = $10,000 (well under the $23,500 cap).
- Employer match: $100,000 x min(10 percent, 6 percent) x 50 percent = $3,000.
- Total year-one contribution: $13,000.
- End of year one balance: $25,000 x 1.07 + $13,000 = $39,750.
- Iterate 30 years with 2 percent annual salary growth.
Projected balance at retirement: about $1,520,000. Of that, Sarah contributed roughly $400,000, the employer added about $122,000, and compounding produced the remaining $1.0 million.
The lesson: at a 30-year horizon and 7 percent returns, every dollar contributed in year one becomes about $7.61 at the end. The employer match is the highest-return investment you will ever make, since it is a 50 percent immediate return on the dollar you contributed.
Frequently asked questions
What is the 2026 401(k) contribution limit?
The IRS employee elective deferral limit for 2026 is $23,500, unchanged from 2025. Workers aged 50 and over can add a $7,500 catch-up for a personal cap of $31,000. A new SECURE 2.0 super catch-up of $11,250 applies to ages 60 to 63, lifting their personal cap to $34,750. The combined employer plus employee limit (415(c)) is $70,000 in 2026.
How is the 401(k) employer match calculated in the calculator?
The model takes the smaller of (a) your contribution percent and (b) the match cap percent of salary, multiplied by the match rate. For example, a 50 percent match on the first 6 percent of salary gives 3 percent of salary as the match. If you only contribute 4 percent, the match drops to 2 percent. The calculator caps employer money at the IRS 415(c) annual additions limit.
What is the 401(k) catch-up contribution for over 50s in 2026?
Workers aged 50 to 59 and 64 plus can add $7,500 on top of the $23,500 base limit, for a personal cap of $31,000. Workers aged 60 to 63 get the SECURE 2.0 super catch-up of $11,250, for a personal cap of $34,750. From 2026 the catch-up portion for high earners (over $145,000 in prior-year wages) must be Roth, not pre-tax.
Should I pick a Roth or Traditional 401(k) in 2026?
Pick Roth if your current marginal tax bracket is lower than your expected retirement bracket. Pick Traditional if it is higher. For most early career workers in the 12 or 22 percent brackets, Roth tends to win because retirement income often lands in the 22 to 24 percent bracket. Splitting 50/50 is a reasonable hedge if you are unsure.
When can I withdraw from a 401(k) without penalty?
The standard age is 59 and a half. Earlier withdrawals usually trigger a 10 percent penalty on top of ordinary income tax, with narrow exceptions: separation from service in the year you turn 55 or later (Rule of 55), substantially equal periodic payments under 72(t), disability, certain medical expenses, and qualified domestic relations orders. RMDs begin at age 73.
How does the 2026 401(k) Roth catch-up rule (SECURE 2.0) affect high earners?
From January 1, 2026, any catch-up contribution by a worker who earned more than $145,000 in FICA wages from the same employer in the prior year must be made on a Roth (after tax) basis. Plans without a Roth option must let high earners forgo the catch-up. The dollar limit is unchanged: $7,500 ages 50 to 59 and 64 plus, or $11,250 ages 60 to 63.
What is the total 401(k) limit including employer match in 2026?
The IRS section 415(c) annual additions limit for 2026 is $70,000 (employee deferrals plus employer match plus after-tax contributions, excluding the catch-up). With the $7,500 catch-up the cap rises to $77,500 for ages 50 to 59 and 64 plus; the $11,250 super catch-up lifts it to $81,250 for ages 60 to 63.
Does the 401(k) calculator factor in fees and inflation?
The annual return field on this page is a nominal rate. To model fees, subtract your plan expense ratio (often 0.10 to 0.75 percent) from the return. To model inflation, use a real return (nominal return minus expected inflation, roughly 2.5 percent long run) so the projected balance is in today's dollars.
