Owner-Only 401(k) Calculator 2026
Calculate your maximum Solo 401(k) contribution as a self-employed owner. Combines the $23,500 employee deferral with the 20%/25% employer profit-sharing, up to the $70,000 total annual additions limit — plus catch-up if age 50+.
The Solo 401(k) Two-Bucket Contribution Limit
The Solo 401(k) (also called Owner-Only 401(k), One-Participant 401(k), or Solo-k) is the most powerful retirement plan for self-employed individuals with no W-2 employees other than themselves and their spouse. For 2026, the contribution limit is structured as two separate buckets that combine: the employee elective deferral of $23,500 (plus $7,500 catch-up if age 50+, or $11,250 super catch-up if age 60-63 per SECURE 2.0), and the employer profit-sharing contribution of up to 25% of compensation. The total combined limit per individual is $70,000 for 2026 (or $77,500 with catch-up, $81,250 with super catch-up). Per IRS guidance on One-Participant 401(k) Plans, the employer side is capped at 20% of net self-employment earnings (after the 50% SE tax deduction) for sole proprietors, or 25% of W-2 wages for S-corp owners.
Sole Proprietor vs S-Corp — The Math Difference
The math for the employer profit-sharing differs by entity. Sole proprietors: net Schedule C earnings × 0.9235 (SE tax adjustment) × 0.20 (the effective 20% rate after factoring in the SE tax deduction). S-corp owners: W-2 wages × 0.25. The S-corp formula produces a larger employer contribution at lower compensation levels, but the S-corp owner must pay the additional payroll taxes on those W-2 wages. Example: $100,000 in net SE earnings as sole prop gives an employer contribution of $100,000 × 0.9235 × 0.20 = $18,470. The same income as $100,000 W-2 wages in an S-corp gives $100,000 × 0.25 = $25,000 employer contribution — a $6,500 difference, but the S-corp owner paid $7,650 in FICA on those wages. The break-even depends on your other distributions vs wages mix.
Spouse Eligibility — Effectively Doubling the Contribution
If your spouse works in the business and is paid wages or has SE earnings, they can maintain their own employee deferral + employer contribution under the same Solo 401(k) plan document. This effectively doubles the household contribution to a maximum of $140,000 for 2026 (or $155,000 with both age 50+ catch-up, $162,500 with both at the super catch-up age 60-63). The spouse must actually perform work in the business — paper-only employment is a red flag for IRS scrutiny. Both employee deferrals and employer contributions count against the individual $70,000 cap, not a combined household cap. This is the Solo 401(k)'s biggest advantage over a SEP-IRA, which only allows employer contributions and has no spouse-doubling option without a separate plan.
2026 Catch-Up Changes — Roth Mandate for High Earners
SECURE 2.0 added a super catch-up of $11,250 for ages 60-63, available 2025+. For 2026, this combines with the regular $7,500 catch-up rules — ages 50-59 get $7,500 catch-up, ages 60-63 get $11,250, and ages 64+ revert to $7,500. A more controversial 2026 change: high-earner catch-up contributions (for those earning more than $145,000 in W-2 wages in the prior year) must be Roth — the pre-tax catch-up is no longer allowed. This rule was delayed from 2024 to 2026 by IRS Notice 2023-62, and forces high earners into the Roth bucket whether they want it or not. Source: IRS 401(k) contribution limits. Last updated May 2026.