Solo 401(k) Employer Contribution Maximizer

Blend net self-employment compensation, your elective deferral, age-based catch-up capacity, and the correct employer percentage to pinpoint how much profit-sharing room is left in your Solo 401(k) for the 2024 plan year.

Net Schedule C income after adjustments or the W-2 wages paid to you from an S-corp that qualify for employer funding.
Salary deferral you plan to contribute for the year (the IRS cap is $23,000 plus a $7,500 catch-up at age 50+).
Determines eligibility for the $7,500 catch-up contribution once you are age 50 or older.
Use 20% for sole proprietors/LLCs (after subtracting half of self-employment tax) or 25% for S-corp W-2 wages.
Defaults to $0.00. Enter half of your self-employment tax so the employer percentage applies to the net earnings worksheet amount.

Solo 401(k) contribution calculations vary with entity structure, earned income, and payroll timing. Confirm final amounts with your tax advisor before funding.

Examples

  • Example 1 — $120,000.00 eligible compensation, $22,500.00 deferral, age 45, 20% employer rate ⇒ Maximum employer contribution: $24,000.00 USD • Total Solo 401(k) funding allowed: $46,500.00 USD • Combined limit remaining: $22,500.00 USD • Limit utilized: 67.39%
  • Example 2 — $180,000.00 eligible compensation, $30,500.00 deferral, age 52, 25% employer rate ⇒ Maximum employer contribution: $45,000.00 USD • Total Solo 401(k) funding allowed: $75,500.00 USD • Combined limit remaining: $1,000.00 USD • Limit utilized: 98.70%

FAQ

Does the calculator enforce the elective deferral limit?

Yes. The elective entry is capped at the lesser of your compensation or $23,000 plus the $7,500 catch-up for age 50+. Any higher number is trimmed before employer dollars are computed.

How do I handle the half self-employment tax deduction?

If you file Schedule C, enter half of your self-employment tax in the optional field so the employer percentage mirrors the IRS worksheet for net earnings from self-employment.

What if my compensation is too low to support the employer contribution?

The employer portion is limited by both your adjusted compensation and the Solo 401(k) annual limit. If either constraint is hit, the result is reduced automatically.

Can I model catch-up contributions separately?

Once you enter an age of 50 or above, the calculator automatically adds the $7,500 catch-up to both the elective deferral cap and total contribution limit.

What if I already contributed to another employer's 401(k)?

Combine all elective deferrals for the calendar year. Because the $23,000 salary deferral cap applies across all plans, reduce the deferral input here by amounts sent to other employers.

Additional Information

  • The model applies the 2024 combined contribution ceiling of $69,000 and automatically adds the $7,500 catch-up allowance for savers age 50 or older.
  • Employee elective deferrals are capped at the lesser of your compensation or $23,000 plus catch-up, ensuring the employer portion is calculated on compliant amounts.
  • Employer funding is limited by the entity-specific percentage (20% for sole props/LLCs, 25% for S-corps) and any half self-employment tax entered.
  • Remaining headroom indicates how much space is still available for discretionary profit-sharing or year-end true-up deposits.
  • Limit utilization shows the share of the annual IRS cap already consumed, helping you schedule additional contributions safely.
  • Outputs assume all compensation is earned from the same trade or business sponsoring the Solo 401(k); unrelated W-2 wages are excluded by design.

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