401(k) Planning Tool
401(k) Withholding Calculator
Find the exact percentage to withhold from your paycheck to max out your 401(k), including catch-up and after-tax spillover contributions.
Built from patterns I see every day working with Fortune 500 employees at companies like AT&T, PG&E, Raytheon, and Honeywell.
No sign-up required · Instant results
Full year planning mode
Planning how to maximize your 401(k) for the full calendar year.
Do you work for one of these companies?
Pick your employer and we'll fill in your exact match details, no guesswork needed.
Your information
Health, dental, HSA, FSA, etc.
Paycheck impact
Here's exactly what changes on your bi-weekly paycheck if you max out vs. staying at your current 6.0%.
Current contribution: 6.0%
Maxed out: 16.3%
Take-home difference
-$453/check
-$11,780/year
Extra to retirement
+$596/check
+$15,500/year
Federal tax reduction
$143/check
$3,720/year
Why is the take-home hit smaller than the contribution increase? Because pre-tax 401(k) contributions reduce your taxable income, your federal tax bill goes down at the same time your contribution goes up. The real cost of maxing out is always less than it looks.
Employee deferral (pre-tax / Roth)
2026 elective deferral limit: $24,500
Set withholding to
16.3%
of gross pay
Max annual deferral
$24,500
Base limit
Per paycheck
$942
Bi-weekly (26/yr)
Estimated tax savings from pre-tax deferral
Based on your 24.0% marginal federal bracket
$5,880
Employer match
4.0% match on the first 6.0% of your salary. Contribute at least 6.0% to capture it all
Annual employer match
$6,000
Employer match dollars
You + employer combined
$30,500
Total pre-tax + match
How the match works: Your employer contributes 4.0% for every 1% you put in, up to 6.0% of your $150,000 salary. That means the most they'll ever match is $6,000, but only if you contribute at least $9,000 yourself.
After-tax spillover (mega backdoor Roth)
The IRS allows total annual additions up to $72,000 (2026 415(c) limit). After your deferral and employer match, you may be able to contribute the remaining room as after-tax dollars and convert to Roth.
Spillover room
$41,500
Available for after-tax contributions
Spillover withholding
27.7%
Additional % of gross pay
Per paycheck (spillover)
$1,596
Bi-weekly (26/yr)
Important: Not all employer plans allow after-tax contributions or in-plan Roth conversions. Check with your plan administrator to confirm eligibility before counting on this strategy.
2026 catch-up contribution rules
| Age group | Base deferral | Catch-up | Total deferral |
|---|---|---|---|
| Under 50← you | $24,500 | N/A | $24,500 |
| Ages 50–59 & 64+ | $24,500 | $8,000 | $32,500 |
| Ages 60–63 (SECURE 2.0)SECURE 2.0 | $24,500 | $11,250 | $35,750 |
SECURE 2.0 note: Starting in 2026, participants ages 60–63 can make an enhanced catch-up of $11,250. For those earning over $145,000, catch-up contributions must be designated as Roth (after-tax).
Your 2026 total contribution summary
Educational estimate based on your inputs and 2026 federal limits, not a prediction of actual results.
Want help optimizing your 401(k) strategy as part of a complete financial plan?
On a $150,000 salary, you could be missing $41,500 of mega backdoor Roth room this year. The actual answer depends on whether your plan allows after-tax contributions and in-plan Roth conversions.
This is an estimate, not a number to plan around alone.
This calculator is an educational tool to help you think through scenarios. The results are illustrative estimates based on the inputs you provided and general assumptions. They are not financial advice, and the numbers shown should not be relied on as exact to your situation.
Real outcomes depend on factors a calculator can't fully model: your complete tax picture, plan-specific rules, market performance, IRS rate changes, life events, and how all the pieces of your financial life interact. Past performance does not guarantee future results.
This tool does not collect, store, or transmit any financial data.
Federal tax brackets shown are based on 2026 rates and may change with future legislation. Employer match calculations are estimates and may differ from your actual plan terms. Farther Finance Advisors LLC is an SEC-registered investment adviser. Registration does not imply a certain level of skill or training.
Before making any decision based on these numbers, let's talk. I'll look at your full picture, pressure-test the assumptions, and help you understand what these numbers actually mean for you, at no cost.
By Jay Chang, VP, Wealth Advisor
Last updated July 6, 2026
What Does a 401(k) Withholding Calculator Do?
It converts the annual IRS deferral limit into the one number your payroll system actually accepts: a percentage of each paycheck. For 2026, the employee deferral limit is $24,500, and most payroll systems only let you elect a whole or fractional percentage, not a dollar target.
This calculator does the division for your exact salary, pay frequency, and year-to-date contributions. It also layers in catch-up eligibility and shows any after-tax spillover room your plan may offer above the deferral limit.
When Should You Recheck Your Withholding Percentage?
Any time the inputs change. The most common triggers I see:
- Every January. The IRS adjusts contribution limits most years. A percentage that maxed you out last year can leave money on the table this year.
- A raise or bonus. Higher pay means the same percentage hits the limit earlier, which can cut off per-paycheck matching in plans without a true-up.
- Turning 50, or entering the 60 to 63 window. Catch-up eligibility adds $8,000 at 50 and older, and SECURE 2.0 raises it to $11,250 for ages 60 to 63.
- A mid-year job change. The deferral limit is per person, not per employer. Your new plan does not know what you already contributed, so you have to set the percentage against what remains.
- Your plan adds after-tax contributions. That opens the door to the mega backdoor Roth, and the spillover percentage becomes part of the same election. I wrote a plan-specific walkthrough for Intel employees in Chandler that shows how this works in practice.
One related caution. If equity compensation is part of your pay, the withholding questions multiply, because the flat 22 percent federal rate applied to vesting RSUs often under-withholds for high earners. I cover that gap in why 22 percent RSU withholding falls short. Getting the 401(k) percentage right is one piece of a larger paycheck strategy, which is the core of my 401(k) planning work.
How to Use This Calculator
- Enter your annual salary, pay frequency, and what you have contributed so far this year.
- Add your age so catch-up contributions apply: an extra $8,000 at 50 and older, or $11,250 at ages 60 to 63.
- Read the exact percentage that maxes out your deferral by year-end, plus what it deducts from each paycheck and the estimated tax savings.
- If your plan allows after-tax contributions, check the spillover section for mega backdoor Roth room above the deferral limit.
401(k) Withholding Questions I Hear Most
What percentage should I withhold to max out my 401(k) in 2026?
Divide the $24,500 deferral limit by your annual salary. On a $200,000 salary, that is 12.25 percent. Add more if you are 50 or older and want the catch-up. The calculator does this math against your exact salary, pay frequency, and year-to-date contributions.
What are the 401(k) contribution limits for 2026?
The employee deferral limit is $24,500. Workers 50 and older can add an $8,000 catch-up. Under SECURE 2.0, workers aged 60 to 63 get an enhanced $11,250 catch-up instead. The combined limit for all contributions, including employer money and after-tax dollars, is $72,000. The IRS publishes the current figures in its 401(k) contribution limit guidance.
Does my employer match count toward the $24,500 limit?
No. That limit applies only to your own pre-tax and Roth deferrals. Employer matching counts against the separate $72,000 combined limit, along with any after-tax contributions you make.
What happens if I max out my 401(k) too early in the year?
It depends on your plan. Many plans match paycheck by paycheck. Hit the deferral limit in September and your contributions stop, and so does the match, unless the plan has a true-up provision that restores the missed match after year-end. Check your plan document before front-loading.
What is after-tax spillover, and how does it relate to the mega backdoor Roth?
Some plans let you keep contributing after-tax dollars once you hit the deferral limit, up to the $72,000 combined cap. If the plan also allows in-plan Roth conversions or in-service withdrawals, you can convert those dollars to Roth. That two-step move is the mega backdoor Roth, and I walk through the full mechanics in my 2026 mega backdoor Roth guide.