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
Want help optimizing your 401(k) strategy as part of a comprehensive 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.
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.
This calculator is for informational purposes only and does not constitute financial advice. 401(k) contribution limits are based on 2026 IRS guidelines and may change. Actual withholding may vary depending on your employer's plan rules, pay frequency, and timing of contributions. Consult with a qualified financial advisor for personalized guidance.