401(k) Calculator (2026)

Why model 401(k) deferrals before you pick a percentage

Choosing a deferral rate from a dropdown is easy; understanding what it does to retirement wealth, employer match, and this year’s tax bill is harder. This calculator projects account growth from your salary, deferral percentage or dollar amount, employer match formula, years to retirement, and assumed return—while respecting 2026 IRS deferral caps.

Traditional 401(k) contributions reduce federal taxable wages now and defer tax until withdrawal. That interacts directly with the federal income tax calculator and paycheck calculator: a higher deferral often means slightly higher take-home pay than you might expect because income tax drops along with Social Security and Medicare wages in typical plans.

2026 contribution limits at a glance

• Employee elective deferral: $24,500
• Catch-up (age 50+): additional $8,000 → $32,500 total deferrals if the plan allows
• Enhanced catch-up (ages 60–63, SECURE 2.0): additional $11,250 where adopted
• IRA (for comparison): $7,500 base; $1,100 catch-up at 50+
• HSA (if on HDHP): $4,400 self-only / $8,750 family; $1,000 catch-up at 55+

These figures come from IRS inflation adjustments (Rev. Proc. 2025-32 and related notices). Your plan may impose lower limits or special rules for highly compensated employees.

Employer match math

Common formulas—50% of deferrals up to 6% of pay, or 100% up to 4%—are free money when you contribute enough to capture the full match. Enter your plan’s match tiers in the tool. Missing match by deferring 3% when the plan matches up to 6% is an immediate negative return no market forecast can fix.

Match dollars usually vest over time. This calculator can show gross match accrual; check your summary plan description for vesting schedules before treating the full balance as portable.

Tax savings this year

Each traditional deferral dollar avoids federal tax at your marginal rate on ordinary income—not at capital gains rates. A worker in the 22% bracket who maxes deferrals below the cap saves roughly $0.22 per dollar in federal income tax, plus payroll tax savings on Social Security (6.2% up to $184,500) and Medicare (1.45%) when deferrals are pre-tax for FICA.

Roth 401(k) deferrals do not appear in that tax-savings column—they are after-tax now. The trade is tax-free qualified withdrawals later. Use the Roth conversion calculator when comparing Roth vs traditional inside the plan or in an IRA.

Growth projection mechanics

Contributions

Annual deferrals plus employer match (and any profit-sharing you model) add to the balance each year. The tool caps employee deferrals at statutory limits including catch-up when you indicate age.

Compounding

Ending balance formulas apply your assumed return to the evolving balance. Sequence-of-returns risk near retirement is not modeled—this is a smooth average path for planning.

Inflation

Nominal dollars at retirement can look large but buy less. Pair results with the retirement calculator for spending needs in today’s dollars if available.

Worked example

Age 45, $110,000 salary, 10% deferral ($11,000), employer matches 50% up to 6% ($3,300 match), 20 years to retirement, 6% average return:

• Employee deferrals stay under the $24,500 cap with room to increase
• Match adds $3,300 annually—$66,000 over 20 years before growth
• Traditional deferrals reduce current taxable wages—run paycheck calculator to see net pay change

At 50, the same worker could add $8,000 catch-up deferrals for an extra $32,500 ceiling. Between 60 and 63, SECURE 2.0 may allow $11,250 catch-up instead—verify plan adoption.

Coordination with other accounts

Maxing 401(k) does not block IRA contributions, but deductibility may phase out. The contribution limits maximizer stacks 401(k), IRA, and HSA room in one view. If you also have a spouse’s plan or self-employment income, see SEP-IRA and Solo 401(k) limits in that tool.

Distribution and RMD planning (high level)

Withdrawals from traditional 401(k) accounts are generally ordinary income. Penalties may apply before 59½ with exceptions. Required minimum distributions begin per SECURE 2.0 age rules. This forward-looking calculator does not model RMDs or early withdrawal penalties—use it for accumulation phase planning.

Common mistakes

• Deferring below the match threshold
• Assuming Roth deferrals reduce current taxes
• Ignoring the $24,500 cap mid-year after front-loading contributions
• Forgetting catch-up eligibility at 50 or enhanced catch-up at 60–63
• Using gross salary instead of plan compensation definition for percentage deferrals

Related tools

See take-home impact in the paycheck calculator. Compare state tax on reduced wages with the state income tax calculator. Stack all retirement buckets in the contribution limits maximizer and HSA calculator.

After-tax vs pre-tax deferral tradeoffs

Traditional deferrals reduce current taxable income; Roth deferrals do not. The right choice depends on whether your marginal rate is higher now or in retirement—a guess about future law and spending. Many plans allow splitting contributions. Mid-career savers often use traditional deferrals for the immediate paycheck boost; early-career workers in lower brackets sometimes favor Roth. Neither choice affects the $24,500 cap.

Loans, hardships, and in-service withdrawals

401(k) loans borrow your own balance and repay with interest to yourself, but default turns the loan into a taxable distribution with possible penalty. Hardship withdrawals narrow to IRS-defined immediate and heavy financial needs. This calculator does not model loan amortization or withdrawal penalties—only accumulation.

Auto-escalation and percentage vs dollar deferrals

Many employers offer auto-escalation that raises deferrals 1% annually until a cap. Dollar deferrals make sense when chasing the exact remaining room in December; percentage deferrals track raises automatically. Revisit percentages after a promotion so you do not silently drift below the match threshold on a higher base salary.

Highly compensated employee (HCE) testing

Plans may limit deferrals for HCEs if rank-and-file participation fails nondiscrimination tests. If your plan notifies you of a refund of excess deferrals, that amount becomes taxable in the year returned—not something this forward calculator predicts.

Employer match formulas in plain language

Partial match formulas confuse people. “50% up to 6%” means the employer adds half of what you defer, but only on deferrals up to 6% of pay—not half of your entire salary. On $100,000 pay, deferring 6% ($6,000) yields $3,000 match; deferring 10% still yields only $3,000 match unless the plan uses a true-up. True-up contributions at year-end fix match when you front-loaded deferrals early. Ask HR for the summary plan description and a match illustration at your exact salary.

Non-elective safe harbor contributions (3% of pay regardless of employee deferral) still count toward your retirement wealth but follow different 415(c) math. Profit-sharing deposits may arrive once annually after year-end testing.

Payroll integration and per-paycheck limits

Plans cap each paycheck at a percentage of gross or a dollar amount. Highly paid workers hit the $24,500 annual cap in fewer periods when deferring flat dollars early. Spread max deferrals across 26 biweekly checks if you want steadier take-home, or front-load when you need cash later in the year for tuition or a home purchase—knowing you may forfeit match true-ups if the plan lacks them.

Target-date funds and allocation inside the plan

Contribution limits apply regardless of investment choice. Target-date funds, company stock, and brokerage windows all share the same deferral cap. Company stock concentration is a separate risk question from tax deferral math.

Spousal beneficiary and survivor planning

Surviving spouses inherit different rollover options than non-spouse beneficiaries under SECURE Act rules. Required beginning dates for RMDs shifted under SECURE 2.0. Accumulation projections here ignore post-death distribution rules—consult estate planning resources when balances are large.

SECURE 2.0 catch-up ages 60–63

For plan years after SECURE 2.0 adoption, participants ages 60 through 63 may defer an additional $11,250 beyond the $24,500 base and the $8,000 age-50 catch-up in eligible plans—instead of stacking both in some designs. Confirm your plan document and SPD; not every employer has amended yet. Enter age in the tool when supported so catch-up ceilings match your birth year.

Tax bracket interaction on deferral increases

Each traditional deferral dollar avoids tax at your marginal ordinary rate. On $95,000 taxable wages as single, moving deferrals from 6% to 15% saves more in the 22% band than in the 12% band for the incremental dollars. Pair deferral changes with the paycheck calculator and federal income tax calculator so you see both retirement wealth and current-year tax, not just account balance growth.

Roth 401(k) inside the plan

Roth deferrals do not reduce current AGI but grow tax-free if qualified. Splitting traditional and Roth deferrals hedges rate uncertainty. The Roth vs traditional IRA calculator uses parallel logic for IRA accounts outside the plan.

Employer profit-sharing and true-up

Non-elective and profit-sharing contributions grow balances without consuming your $24,500 elective room but count toward 415(c). Year-end true-up deposits can surprise you with higher balances than paycheck deferrals alone suggest—check SPD annually.

Catch-up at 50 and enhanced 60–63

Age 50 unlocks $8,000 catch-up on top of $24,500. SECURE 2.0 may allow $11,250 enhanced catch-up for ages 60–63 when the plan adopts it—enter age accurately so projections do not understate deferral capacity.

Planning takeaway

Maximizing deferrals lowers AGI for the federal income tax calculator and increases take-home precision in the paycheck calculator. Revisit deferral percentage after every raise so match thresholds scale with new base pay.

Sources and methodology

Deferral and catch-up limits follow IRS 2026 cost-of-living adjustments. Growth projections are deterministic compound math for education—not investment advice.