How the 401(k) calculator works
Enter your salary, the percentage you contribute, your employer's match formula, your current balance and an expected return. Each year the calculator works out your contribution, applies the 2026 IRS limits, adds the employer match, spreads the money over 12 monthly paychecks and grows the balance at your return rate. Your salary rises by the yearly raise you enter, so contributions grow with it.
Example: a 30-year-old earning $75,000 who contributes 10% with a 50% match up to 6% of pay, a $10,000 starting balance, 3% raises and a 7% return would have about $2,084,041 at 65, or $878,155 in today's dollars at 2.5% inflation. Of that, $453,466 comes from their own contributions and $136,040 from the employer.
How an employer match works
A match is money your employer adds when you contribute. A common formula is "50% of your contributions up to 6% of pay": contribute 6% or more and the employer adds 3% of your salary. In the example, the match adds $456,294 to the final balance compared with no match at all.
If you contribute less than the match limit, you leave free money behind. Someone earning $60,000 with a dollar-for-dollar match on the first 6% who contributes only 3% misses $1,800 of match a year. The calculator tells you when that happens. Employers may also make a non-matching contribution, such as a 3% safe harbor contribution; enter it as "other employer contribution". Many plans have a vesting schedule, so check how long you must stay to keep employer money.
2026 401(k) contribution limits
For 2026 you can defer up to $24,500 of your pay into a 401(k), 403(b), governmental 457 plan or the Thrift Savings Plan, up from $23,500 in 2025. If you are 50 or older you can add a $8,000 catch-up, for $32,500. Under SECURE 2.0, people aged 60, 61, 62 or 63 get a higher catch-up of $11,250, for $35,750 in total (IRS IR-2025-111).
On a $150,000 salary with a high contribution rate, a 52-year-old can put in $32,500 and a 61-year-old $35,750. The combined total from you and your employer is capped at $72,000 a year, not counting catch-up contributions, and only the first $360,000 of pay counts toward plan contributions. From 2026, if your FICA wages from the employer were more than $150,000 in 2025, your catch-up contributions must go in as Roth contributions (IRS Notice 2025-67 (2026 cost-of-living adjustments)).
How much should you contribute?
Contributing at least enough to get the full match is the usual first step. Beyond that, each extra percentage point compounds: raising the contribution from 10% to 15% in the example grows the balance from $2,084,041 to $2,844,532, while dropping to 6% leaves $1,475,649.
Traditional (pre-tax) contributions lower your taxable income now and are taxed when you withdraw them; Roth 401(k) contributions are made after tax and qualified withdrawals are tax-free. Both count toward the same $24,500 limit. To see how a pre-tax contribution changes your take-home pay, try the paycheck calculator; for tax-free growth outside work, see the Roth IRA calculator. Saving in India instead? The PPF calculator shows a comparable long-term scheme.
Why starting early matters
Time does much of the work in a 401(k). With the same salary, contribution rate and match as the example, someone who starts at 25 instead of 30 would have about $3,095,123 at 65, and someone who starts at 40 about $892,604, because they contribute for 25 years instead of 35. Each early dollar has more years to compound.
If you are behind, the catch-up contributions from age 50, and the larger ones from 60 to 63, are designed to help you save more in the final years before retirement. Tick the catch-up box and raise your contribution percentage to see the effect.
What the estimate does not include
The balance is before income tax on withdrawals and before any investment fees, which reduce returns. Returns are shown as a steady average, while real markets rise and fall. IRS limits are held at 2026 amounts, although they normally rise with inflation, and early withdrawals before 59½ may face tax and a 10% additional tax. Treat the result as a planning estimate, not investment advice.