Pensions & Social Security
Raise the 401(k) contribution: what happens to the paycheck?
A 401(k) contribution paycheck calculator: employees see that a bigger pre-tax contribution cuts take-home pay by less than the contribution, because of the tax saved.
Included in Network. 14-day trial, cancel any time.
How much will increasing my 401(k) contribution reduce my paycheck?
Less than the contribution. A pre-tax contribution lowers taxable pay, so the paycheck falls by the contribution minus the income tax saved. At a 22% marginal rate, an extra $100 contribution reduces take-home pay by about $78. The 2026 deferral limit is $24,5002026 · IRS.
January, when new contribution rates start
People want to save more but worry about the paycheck. At open enrollment and after a raise, they hesitate over a few percentage points. Seeing the actual change per paycheck is often what gets them to act.
What the client types into a search box
“how much will my paycheck go down if I contribute more to my 401k”
How a client works through it
Enter gross pay per period
Pay before deductions for one paycheck.
Choose pay frequency
To annualize the results.
Enter marginal rate
The rate that sets the tax saving.
Enter current and new contribution
Percentages of pay, before and after the change.
What lands in your inbox
When a client asks your firm to review the result, the request arrives as a contact record with their inputs and results attached, by email and, on paid plans, by webhook to your CRM.
Received
Gross pay, frequency, marginal rate and the current and new contribution percentages show income and savings intent. A large jump in contribution rate suggests a client motivated to save, perhaps after a planning conversation; a high earner near the limit may need catch-up or Roth advice.
Why does take-home fall by less than the contribution?
Extra Contribution per Period is the added saving. Tax Savings per Period is the income tax no longer withheld on it. Net Paycheck Reduction is the difference, the real cost to the paycheck.
New Annual Contribution lets the client check the total against the annual limit.
Results shown: Net Paycheck Reduction · Extra Contribution per Period · Tax Savings per Period · New Contribution per Period · Annual Extra Contribution · New Annual Contribution.
A 2-point increase
On $3,000 of gross pay per period, going from 4% to 6% adds $60 per period. At a 22% marginal rate, tax withheld falls by $13.20, so take-home drops by $46.80. Over 26 pay periods, that's $1,560 more saved for $1,216.80 less take-home.
Why is this a useful employer-client tool?
Firms with business clients can offer it to those clients' employees during enrollment, improving plan participation, which helps plan testing and employee outcomes. For individual clients, it turns a vague intention into a specific change.
It also shows a firm's understanding of the tax mechanics in a friendly way.
Follow-ups this request opens
- Set contributions to capture the full match
- Plan Roth versus pre-tax contributions
- Check the deferral limit for high earners
- Adjust withholding after the change
What this calculator leaves out
- Uses a flat marginal rate, not the full bracket schedule.
- FICA is not reduced by 401(k) contributions and isn't shown.
- State tax savings are not included unless added to the rate.
- Roth contributions don't produce the tax saving shown.
Platform disclaimer shown under the calculator: Estimates only. Pre-tax contributions lower taxable income, so take-home pay drops by less than the contribution. Uses a flat marginal rate; real payroll taxes and brackets differ.
Compliance note for firms
Showing the paycheck effect is education; recommending a contribution rate is advice. For employer-sponsored plans, firms advising participants should be mindful of fiduciary obligations under ERISA where applicable.
Not legal advice. See our disclaimer and the guide to compliance for client calculators.
2026 figures this page relies on
| Figure | Value | Tax year | Source |
|---|---|---|---|
| 401(k)/403(b)/457(b) employee deferral limit | $24,500 | 2026 | IRS |
The same values drive the calculator. Full list on the 2026 figures page.
Terms your client sees in the calculator
These definitions appear in the calculator's collapsible Definitions block, so clients don't have to call to ask what a label means.
- Pre-tax contribution
- Money taken from your paycheck for a 401(k), 403(b) or similar plan before income tax is figured. Because it lowers taxable income, take-home pay falls by less than the amount contributed. Pre-tax contributions are still subject to Social Security and Medicare tax, and the money is taxed as income when you withdraw it later.
- Net paycheck reduction
- How much your take-home pay actually drops each pay period after the change: the extra contribution minus the income tax you no longer pay on it. It is the practical figure for budgeting, because it is the only part that leaves your spending money, while the full extra contribution goes into your retirement account.
- Marginal tax rate
- The rate applied to your last dollar of income; here, your combined federal and state marginal rate. It sets the tax savings on each extra dollar contributed: at 22%, raising a pre-tax contribution by $100 cuts income tax by about $22, so the paycheck drops by about $78. It is usually higher than your average tax rate.
- Contribution percentage
- The share of gross pay you elect to send to your retirement plan each pay period. The calculator compares your current percentage with a new one. The IRS caps annual employee elective deferrals, $24,500 for 2026 (IRS, 2026), so a high percentage on a high salary can reach that cap before the year ends.
- Gross pay
- Your earnings for a pay period before any taxes or deductions. Contribution percentages are applied to this figure, so a 6% contribution on $3,000 of gross pay is $180 per period. Whether bonuses or overtime count toward the contribution base depends on your plan’s rules, which this calculator does not model.
- Pay frequency
- How many paychecks you receive per year: 52 weekly, 26 biweekly, 24 semimonthly or 12 monthly. The calculator multiplies per-period figures by this number to produce the annual totals. Biweekly pay gives 26 checks, not 24, which matters when you convert a per-check amount into a yearly contribution.
In our glossary: Elective deferral · Marginal tax rate
Contribution Effect on Your Paycheck calculator: questions from firms and clients
Does a 401(k) contribution reduce Social Security tax?
No. Pre-tax 401(k) deferrals still count as wages for FICA.
What's the 2026 limit?
$24,5002026 · IRS for employee deferrals.
Does a Roth contribution have the same effect?
No. Roth contributions are after tax, so take-home falls by the full amount.
Does the match change my paycheck?
No. The employer's match is added to the account, not deducted from pay.
Can I include state tax savings?
Yes, by entering a combined federal and state marginal rate.
What if I hit the limit early?
Contributions stop for the rest of the year, and some plans then miss match. Spread contributions evenly if the plan has no true-up.
Is this useful for employers?
Yes, as an enrollment education tool.
Which plan includes it?
Network. See pricing.
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Clients who ask this usually ask next
401(k) / 403(b) / 457
how much should I contribute to my 401k to get the full match
Take-Home Paycheck
why is my paycheck smaller this year and what will I actually take home
Roth vs. Traditional
should I choose roth or traditional 401k
All “Pensions & Social Security” calculators · Everything in Retirement
Next entry
Answer the January question before the client calls
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