How to use the 401(k) calculator
The Growth tab projects the account to retirement. The Paycheck impact tab shows what a contribution costs you today.
- Age and retirement age. Whole years. The calculator steps through each year until retirement and applies the catch-up you qualify for at each age.
- Salary and salary growth. Your current base pay and the average yearly raise you expect.
- Your contribution and current balance. The percentage of salary you defer, traditional and Roth combined, and what the account holds today.
- Employer match. Enter the formula from your plan’s summary: the match rate and the share of salary it applies to. “50% of the first 6%” is 50 and 6; “dollar for dollar up to 4%” is 100 and 4. Add any non-elective contribution your employer pays regardless of what you do.
- Return, fees and inflation. The return before fees, the total of fund expense ratios and plan fees, and an inflation rate that converts the result to today’s dollars.
On the Paycheck impact tab, enter your salary, pay frequency, contribution rate, filing status, age and a flat state tax rate, and choose traditional or Roth.
How the projection works
Each year, the calculator works out what you and your employer put in, then grows the balance:
Match = Match rate × min(You, Match cap % × Salary)
Balanceend = Balancestart × (1 + r − fee) + (You + Match + Non-elective) × growth for part of the yearContributions go in monthly, so each one earns a partial year of return. The salary used for employer money is capped at the $360,000 compensation limit, and employee plus employer contributions are capped at $72,000 (catch-ups are on top).
A worked example
An employee who is 35 years old earns $85,000, contributes 6% of salary and has $40,000 saved. The employer matches 50% of contributions up to 6% of salary.
This year the employee puts in $5,100 and the employer adds $2,550, so $7,650 goes into the account. With 3% raises, a 7% return and 0.5% in fees, the balance at 65 years is $1,206,711, or $575,290 in today’s dollars at 2.5% inflation.
Of that total, the employee contributed $242,635, the employer $121,317 and investment growth supplied $802,759, which is 67% of the final balance.
Don’t leave the match on the table
An employer match is an instant return on the money you put in, before any market gain. With a 50% match, every dollar up to the cap becomes $1.50 the day it is invested. No fund offers that, which is why the usual first step in retirement saving is to contribute at least enough to get the full match.
The calculator warns you when your rate falls short. At 3% instead of 6%, the example employee misses $1,275 a year of employer money. Over a career the gap compounds:
| Contribution rate | Employer adds in total | Balance at 65 years | In today’s dollars |
|---|---|---|---|
| 3% | $60,659 | $735,643 | $350,712 |
| 6% | $121,317 | $1,206,711 | $575,290 |
| 10% | $121,317 | $1,625,438 | $774,916 |
| 15% | $121,317 | $2,148,847 | $1,024,447 |
Going from 3% to 6% doubles both what you save and what the employer adds. Above 6%, the match stops growing, but your own savings still compound. Check how your plan calculates the match: some match each paycheck, so if you hit the annual limit early in the year, you can lose the match on later paychecks unless the plan makes a “true-up” contribution after year-end.
Catch-ups and the age 60–63 super catch-up
From age 50 the limit rises by $8,000. SECURE 2.0 added a larger catch-up of $11,250 for the years you turn 60, 61, 62 and 63; at 64 you drop back to the regular catch-up. These extra amounts are not counted against the $72,000 employee-plus-employer cap.
At 50 years old, an employee earning $120,000 wants to contribute 30% of salary, more than the limit allows from the first year, at age 50. The calculator caps each year at the limit for that age, including 4 years at the higher age 60–63 amount. Starting from $150,000, the account reaches $1,436,377 by 65 years, or $991,769 in today’s dollars.
If your wages from the employer last year were above $150,000, catch-up contributions must be Roth. That does not change the projection here, which treats traditional and Roth money alike, but it does change the tax saving you get on the Paycheck impact tab.
Fees matter more than they look
A fee of half a percent sounds small, but it is charged on the whole balance every year for decades. In the example, the 0.5% fee costs $120,836 by retirement, 9% of what the account would hold with no fees.
| Annual fees | Balance at 65 years | Cost of fees |
|---|---|---|
| 0.1% | $1,302,308 | $25,238 |
| 0.5% | $1,206,711 | $120,836 |
| 1% | $1,098,388 | $229,158 |
Your plan’s fee disclosure lists the expense ratio of each fund. Broad index funds often charge well under 0.2% a year; actively managed funds usually charge more.
What a contribution does to your paycheck
A traditional contribution comes out before income tax, so it lowers your take-home pay by less than you save. In the default example, contributing 6% of $85,000 puts $196.15 per paycheck into the plan, yet take-home pay falls by only $145.15, because income tax falls by $1,326.00 over the year. Each dollar saved costs $0.74 of spending money.
| Option | Contribution per paycheck | Change in take-home pay | Tax saved this year |
|---|---|---|---|
| Traditional, 6% | $196.15 | -$145.15 | $1,326.00 |
| Roth, 6% | $196.15 | -$196.15 | $0.00 |
| Traditional, 10% | $326.92 | -$241.92 | $2,210.00 |
The Roth costs more today, but the money it builds is not taxed again in retirement. For a married employee aged 61 earning $200,000 and contributing 20%, the limit is $35,750, and the $11,250 catch-up must be Roth because the wages exceed $150,000: only the first $24,500 lowers the tax bill.
What this calculator does not include
- Limit changes. Real limits rise in $500 steps when inflation allows; the projection indexes them smoothly.
- Vesting. Employer contributions may take several years to become yours. Leaving early can forfeit part of them.
- Taxes on withdrawal. Balances are shown before tax. Traditional money is taxed as income when withdrawn, and withdrawals before 59½ usually add a 10% penalty.
- Market swings. A steady return hides bad years; the order of returns matters most near retirement.
- State rules. The paycheck tool uses one flat state rate. A few states, such as Pennsylvania, tax 401(k) contributions, and FICA is never reduced.
Treat the result as a planning estimate, and check your plan documents for the exact match formula and fees.