401(k) growth, in short
A 401(k) calculator projects your balance at retirement by adding up three things every year: what you contribute from your paycheck, what your employer adds as a match, and investment growth on the running total. The employer match is the part worth paying closest attention to — it's money you only get if you contribute enough to trigger it, and missing it is the single most common way people leave value on the table.
Key takeaways
- On a $60,000 salary contributing 6% for 35 years with a 50% match up to 6% and a 7% return, the projected balance is roughly $1.03 million — over 70% of it from investment growth, not contributions.
- Contributing only 3% instead of the full 6% match limit doesn't just cost you 3% of pay — it roughly halves your projected ending balance, since you also forfeit half the employer match.
- Starting at 25 instead of 30 — same salary, same contribution rate — adds about $495,000 to the same projection, purely from five extra years of compounding.
- IRS contribution limits and catch-up allowances (shown in the sidebar) are applied automatically and change most years, so treat them as a reference point, not a fixed number.
- This tool assumes one constant annual return the whole way through — real markets move up and down year to year, so treat the projection as a planning estimate, not a promise.
What a 401(k) balance is actually made of
Every dollar in a 401(k) traces back to one of three sources: money you contributed from your paycheck, money your employer added as a match, and investment gains on top of both. Employers typically match a percentage of what you put in, up to a cap expressed as a percentage of salary — for example, 50 cents per dollar you contribute, up to 6% of pay. Contribute less than that cap and you still get matched, just proportionally less; contribute at or above it and you've captured the full match available to you.
How this calculator projects your balance
Each year, the calculator works out your contribution (salary × contribution %, capped at the IRS limit), the matching employer contribution, and then applies your expected annual return to the running balance. Salary is increased each year by your assumed raise percentage before the next year's contribution is calculated.
Using the calculator's defaults — a 30-year-old earning $60,000, contributing 6% with a 50% match up to 6% of salary, a 2.5% annual raise, and a 7% return, retiring at 65 — the 35-year projection breaks down like this:
Projected balance at 65: ≈ $1,031,279
Your contributions: ≈ $197,742
Employer match: ≈ $98,871
Investment growth: ≈ $734,667
Notice that growth outweighs contributions by more than 2 to 1. That's the part a 401(k) projection makes visible that a simple savings estimate doesn't: over 35 years, the market does more of the heavy lifting than your paycheck does.
What it costs you to under-contribute
Since the employer match scales with your own contribution up to the limit, contributing below that limit doesn't just shrink your own savings — it shrinks the match too. Take the same $60,000 example, but drop the contribution rate from 6% to 3%, still with a 50% match up to 6% of salary:
At 6% contribution: employer match ≈ $98,871 → ending balance ≈ $1,031,279
At 3% contribution: employer match ≈ $49,435 → ending balance ≈ $515,640
Halving the contribution rate roughly halves the final balance — not just because you put in less, but because you also gave up half the free money your employer was offering. If your budget can only stretch to part of the match limit, that gap is worth closing before funding almost anything else.
Why starting five years earlier is worth six figures
Compounding rewards time more than it rewards a bigger check. Keep every other assumption the same — $60,000 salary, 6% contribution, 50% match up to 6%, 7% return — and just move the start date from age 30 to age 25. That's five extra years of growth on a smaller, younger balance, and it adds roughly $495,000 to the age-65 projection: about $1.53 million instead of $1.03 million. Delaying by the same five years works in reverse — it's one of the more expensive forms of procrastination.
IRS limits and catch-up contributions
The IRS caps how much you personally can contribute to a 401(k) each year, and that cap typically rises with inflation. Workers age 50 and up can add a catch-up contribution on top of the standard limit, and current law gives workers age 60 to 63 an even higher catch-up allowance. This calculator applies the limit figures shown in the sidebar automatically when you check the catch-up box — but because these numbers are set annually, always confirm the limit for the specific tax year you're contributing in rather than assuming last year's figure still applies.
Where this projection can go wrong
This calculator assumes one steady annual return for every year between now and retirement. Real markets don't work that way — returns swing year to year, and a downturn in the years right before retirement can matter more than the same downturn decades earlier. The projection also doesn't account for fund fees, job changes and vesting schedules on employer contributions, or changes to your contribution rate over time. Treat the final number as a directional estimate for planning, not a guarantee.
Related calculators
If you're weighing Roth vs. traditional contributions, the Roth IRA calculator and IRA calculator cover the accounts you can fund alongside or instead of a 401(k). For the bigger retirement-income picture, the retirement calculator and Social Security calculator help estimate what your 401(k) balance needs to cover versus what other income sources will provide.