What a 401(k) projection shows
A 401(k) projection answers one planning question: if you keep contributing at a steady rate until a chosen retirement age, and your employer matches part of it, roughly how large could the account be? This calculator takes your annual eligible pay, your current balance, your age and retirement age, your contribution rate, the two tiers of your employer match and an assumed annual return. It returns the projected balance, how that balance divides between your own contributions, the employer match and investment growth, and a year-by-year schedule you can read or download.
The default example is a 75,000 salary, a 6% contribution, a match of 50% on the first 3% of pay plus 20% on the next 3%, a 6% effective annual return and a start at age 30 with 35,000 already saved. In the first year you contribute 4,500.00 and the employer adds 1,575.00. Held to age 65, that plan reaches 945,979: 157,500 from you, 55,125 from the employer and 698,354 of growth. The return is an assumption, not a forecast, and the result is in nominal dollars with no allowance for inflation, fees or tax.
How the employer match is calculated
Employer matches usually work in tiers. In the default plan the employer pays 50 cents on each dollar you contribute up to 3% of your pay, then 20 cents on each further dollar up to a cumulative 6%. At 75,000 pay, 3% is 2,250 and 6% is 4,500. Putting in the first 2,250 earns 1,125.00 of match, and the next 2,250 earns 450.00 more, so a contribution of 4,500 captures the full 1,575.00. Contributing more than 6% adds nothing to the match under these tiers: at 10% you put in 7,500.00 and the match is still 1,575.00.
The calculator applies those tiers paycheck by paycheck, the way a payroll system would. With 24 pay periods, each paycheck is 3,125.00 of pay, your contribution on it is 6% of that, and the match is worked out on that paycheck alone. Entering a lower rate shows how much match is left unclaimed. At a 3% contribution the match is 1,125.00 instead of 1,575.00, so 450.00 a year is not captured. Setting both match rates to 0 shows the account without any employer money: the same plan then ends at 770,470, which is 175,510 lower.
The yearly cap and the true-up
The tax law limits how much an employee can defer into a 401(k) each year. For 2026 the IRS lists 24,500, with a catch-up of 8,000 for participants age 50 or over if the plan allows it, and 11,250 for ages 60 to 63. Your plan may set a lower limit. The calculator therefore lets you type the yearly cap you want to model. It is held constant for every year of the projection, not raised for inflation, because future limits are not known.
The cap matters for the match when someone contributes heavily early in the year. Take a 12,000 salary paid monthly, a 100% contribution, a 6,000 cap and a match of 100% of the first 6% of pay. The cap is reached after six paychecks. Each of those six earns 60.00, so the match paid during the year is 360.00. The remaining six months have no contribution and no match. A plan with a year-end true-up compares what was paid with what the whole year entitles: the entitlement is 720.00, so the true-up adds 360.00 and the total match becomes 720.00. Not every employer pays a true-up, so it is off by default here; turn it on only if your plan documents say so.
Assumptions and what is not modelled
The model is deliberately simple so that every number can be checked. Pay is spread equally over the pay periods of each full year, your contribution rate is constant within a year, you stay with the same employer, and the return is a constant effective annual rate applied once a year, with contributions added at the end of each year. Pay growth is an optional assumption: at 3% a year the default plan ends at 1,255,638, against 945,979 with flat pay.
The calculator does not model the overall limit on all contributions to your account, the limit on pay a plan can count (360,000 for 2026), vesting schedules, Roth catch-up rules for higher earners, contributions to other plans, early withdrawals, loans, taxes or fees. It does not decide whether you are eligible for catch-up contributions. These rules differ by plan, so treat the output as an estimate and read your plan documents.
Why starting early matters
Time does more than contribution size. The default plan starts at 30 and reaches 945,979 at 65. Starting the same plan at 45, with the same balance and a 20-year horizon, ends at 335,722. The assumed return is a large lever too: at 3% a year the default plan reaches 465,792 and at 8% it reaches 1,564,312. A projection is a range of outcomes depending on one assumption, not a single answer. In the default plan a true-up changes nothing (0.00), because the cap is never reached and every paycheck already earns its full match.
To go further, see how regular saving behaves in the compound interest calculator, estimate how much you may need in the retirement planning calculator, or work out the saving rate a target requires with the required savings rate calculator.
Frequently asked questions
How much should I contribute to get the full employer match?
Contribute at least the highest share of pay your plan matches. In the default plan that is 6% of pay, because the second tier ends there. A lower rate leaves part of the match unclaimed, and a higher rate does not raise it.
Does the employer match count toward my contribution limit?
The IRS limit on employee elective deferrals applies to your own contributions, not to the employer match. A separate overall limit applies to the total going into your account, including the match. This calculator checks only the yearly cap you enter.
What is a true-up and does my plan have one?
A true-up is a year-end payment that brings your total match up to what the whole year entitles you to, when contributing early in the year or reaching the cap would otherwise have lowered it. Some plans pay it and others do not, so ask your plan administrator.
Which return should I enter?
Use a cautious figure after fees and run a low and a high case. The calculator holds the return constant, whereas real returns vary from year to year, so the order of returns is not captured.
Is the result guaranteed or tax advice?
No. It is an illustration under the stated assumptions. It does not account for taxes, vesting or changes to your pay, plan or the law, and it does not promise a return. See the disclaimer.
Sources
Contribution limits: IRS, Retirement topics: 401(k) and profit-sharing plan contribution limits (page reviewed by the IRS on 8 April 2026, read on 2 November 2026). The 2026 limits are labelled for that year only and are not assumed for any other year.