401(k) Combined Contribution Calculator
Model how much room may remain under the 2026 total additions cap after employee deferrals and employer contributions—before after-tax or mega backdoor strategies.
Plan additions
Simplified model aligned with this site’s 2026 limits page: total additions caps move with catch-up eligibility. Your plan document controls definitions of compensation and excluded pay types.
How to Use the 415(c) Headroom Tool
Enter amounts your plan actually allocates to you for the plan year—employer contributions are often higher than “match rate” alone suggests once profit sharing is included.
- Separate deferrals from employer money. Employee elective deferrals and employer contributions share the broader additions cap in this simplified view.
- Compare to mega backdoor planning. After-tax contributions typically consume remaining Section 415 room—if your plan allows them.
How to Read the Results
Not a compliance test
Actual testing (ACP, ADP, top-heavy) can further constrain contributions.
What to Do Next
How We Reviewed This Tool
Tool-Level Methodology
- Modeled Section 415(c) headroom as total additions minus employee deferrals minus employer contributions, then lifted the ceiling using the same catch-up-adjusted totals used in the 2026 FAQ copy.
- Positioned the mega backdoor calculator as the natural next step when readers still have positive headroom.
- Flagged ADP/ACP/top-heavy testing as out of scope so advanced plan testing is not silently assumed away.
Assumption Review
- Employer contributions are entered as an annualized total; forfeiture allocations and off-cycle true-ups may shift real totals.
- Different plan types can define compensation differently; this is a planning estimate tied to IRS headline caps, not a compliance test.
- After-tax contributions are not automatically allowed just because headroom exists.
Update Log
- Added the combined limit tool to connect employer match dollars with total plan additions framing.
- Aligned catch-up-adjusted totals with the catch-up calculator and mega backdoor pages.
- Linked back to the IRS limits article for readers who need primary-source context.
Section 415(c) in Plain English
Most workers hear only about the $24,500 employee limit. The separate combined cap matters when you receive large employer contributions or want to stack after-tax savings.
Frequently Asked Questions
What is Section 415(c) for a 401(k)?
Section 415(c) caps total annual additions to your account from employee deferrals, employer match, and other employer contributions in a defined contribution plan. For 2026, the base limit is $70,000, with higher totals when catch-up contributions apply.
Are catch-up contributions included in the $70,000 limit?
Under current IRS guidance for 2026, catch-up contributions can increase the total additions ceiling (for example, up to $78,000 for many age 50+ savers, or $81,250 for ages 60–63). Your plan document still controls what sources count toward each slice.
What happens if I exceed the combined limit?
Excess contributions may need to be corrected through returned deferrals or other plan fixes and can have tax consequences. Use this tool as a planning estimate and verify with your plan administrator.
How we document this page (E-E-A-T)
Experience. This page is written for U.S. workers navigating real payroll and plan rules, not abstract theory. Where we simplify, we say so explicitly so you can escalate to your plan’s summary plan description (SPD) or recordkeeper.
Expertise. 401lcalculator.com is an independent retirement planning tool site founded by David Jones (calculator methodology specialist). Limits and formulas are checked against IRS retirement-plan notices and SECURE 2.0 framing. Numeric caps align with our 2026 limits reference page, which cites Notice 2025-67.
Authoritativeness. For any conflict between this calculator and the IRS or your plan, the IRS and your plan win. Primary sources:
- IRS — Retirement Topics, 401(k) and profit-sharing plan contribution limits
- IRS Notice 2025-67 (PDF) — official 2026 dollar announcements.
Section 415(c). Combined additions limits interact with plan design, compensation definitions, and nondiscrimination testing. This calculator is a headline-cap remainder estimate only—not ADP/ACP or top-heavy testing.
Trustworthiness. This tool is not individualized tax, legal, or wealth-management advice. Plan documents, payroll settings, and your full tax return facts can change outcomes. We publish calculator methodology in the sections above so you can compare our framing with your plan administrator or a licensed professional.
For one-on-one guidance, consult a CFP® professional. All math runs locally in your browser; see our privacy policy.
Corrections. If you believe a limit or IRS reference is out of date after publication, please contact us with a primary source link so we can verify and update.
- Reviewed by David Jones
- Limits Updated for 2026 IRS contribution caps
- Formulas Verified quarterly
Review & Methodology
- Reviewed by David Jones (calculator methodology).
- Updated for 2026 IRS contribution limits (refreshed after each annual IRS notice).
- Core calculator formulas are re-tested quarterly; limit-driven logic is checked when IRS guidance changes.
- Educational projections only — not investment, tax, or wealth-management advice. Calculations run locally in your browser.