Most 401(k) calculators ask for a monthly contribution and silently assume it never changes. Real 401(k)s don't work that way: you contribute a percentage of a salary that grows, and your employer matches only up to a cap. This calculator models both, deducts fund fees from returns every year, and shows the full year-by-year table so you can audit the growth instead of trusting it.
How this projection works
Each year, four things happen in order: your balance grows by the net return (annual return minus the expense ratio), you contribute your deferral percentage of that year's salary, your employer adds the match on your contribution up to the match limit, and your salary grows by the salary-growth rate. Repeat for the number of years you enter.
The match matters more than most people expect: a 100%-up-to-4% match on a $95,000 salary is $3,800 a year of free money in year one — and it compounds for the entire horizon.
balance[n] = balance[n-1] × (1 + return − fee)
+ salary[n] × deferral
+ min(salary[n] × deferral, salary[n] × matchLimit) × matchNote the fee: a 0.35% expense ratio doesn't sound like much, but it is charged against the whole balance every year. On this page's sample it silently costs more than a year of salary over 25 years. Find your real fee in your fund prospectus and enter it.
The sample, end to end. You have $85,000 saved, earn $95,000, defer 10%, and get a full 4% match at 7% returns with a 0.35% fee. After 25 years you have $1,484,246. You and your employer put in $484,908 combined — growth did the other $999,338. By year 10 the balance is $365,810; the compounding curve is where the action is.
Terms & definitions
Elective deferral
The percentage (or dollar amount) of your salary you choose to contribute to the plan.
Employer match
Money your employer adds, usually a percentage of your own contribution up to a cap — e.g. 100% up to 4% of pay.
Expense ratio
The annual fee a fund charges, as a percentage of assets. Charged against the whole balance every year.
Vesting
When employer contributions become yours unconditionally. Your own contributions are always 100% vested.
Frequently asked questions
Does this include catch-up contributions?
Indirectly. For 2026 the IRS elective deferral limit is $24,500 ($32,500 if you're 50+, or $35,750 at ages 60–63 under SECURE 2.0). If you max out, just set your deferral percentage to the equivalent of your actual dollar amount divided by salary — e.g. $24,500 on a $150,000 salary is 16.3%.
What return should I use?
We default to 7% — roughly a blended long-run stock/bond average before inflation. Stocks alone have averaged higher, bonds lower. Use whatever matches your actual allocation, then stress-test it: change 7% to 5% and see how the ending balance moves. Planning on a range beats planning on a point.
Does the employer match vest immediately?
The calculator assumes every matched dollar is yours. In reality some plans vest employer contributions over 2–6 years. If you might leave before full vesting, treat part of the employer line as provisional.
Is this pre-tax or Roth 401(k)?
The projection is identical for traditional and Roth 401(k)s — same contributions, same growth. What differs is tax treatment at withdrawal, which this calculator deliberately leaves to you and the withdrawal calculator.
References
- IRS — 401(k) and profit-sharing plan contribution limits: irs.gov/retirement-plans/plan-participant-employee/retirement-topics-401k-and-profit-sharing-plan-contribution-limits
- IRS Newsroom IR-2025-111 — 2026 limits ($24,500 deferral; $8,000 catch-up; $11,250 ages 60–63)
- Investor.gov — compound interest calculator and fundamentals: investor.gov