Solo 401(k) Contribution Calculator

What Is a Solo 401(k)?

A Solo 401(k) is a retirement plan designed for self-employed individuals and owner-only businesses with no full-time employees other than a spouse. Because you play both roles — employee and employer — you can contribute in two ways, which lets Solo 401(k) savers shelter far more income than a traditional IRA or SEP-IRA at the same earnings level. This calculator uses the 2026 IRS limits to show your exact maximum contribution.

2026 Contribution Limits

For 2026, the employee elective deferral limit is $23,500 (or $31,000 if you are age 50 or older, including the $7,500 catch-up). The employer profit-sharing piece is up to 25% of net self-employment earnings. The combined annual additions limit is $70,000, or $77,500 with catch-up. "Net self-employment earnings" means net Schedule C profit minus half of self-employment tax — the calculator handles that adjustment automatically.

Employee vs Employer Contributions

The employee portion is a flat-dollar deferral you can make up to the elective limit regardless of income. The employer portion is a percentage of earned income — effectively 20% of net self-employment earnings after the SE tax adjustment, which equals 25% of the post-contribution base. Maxing both is how Solo 401(k) holders routinely shelter $60,000+ in a single year. Roth Solo 401(k) variants let you designate the employee portion as after-tax for tax-free growth.

Solo 401(k) vs SEP-IRA

At lower incomes, Solo 401(k) lets you save much more because the $23,500 employee deferral is not tied to income. A SEP-IRA only allows the 25% employer piece, so at $50,000 net SE income the SEP caps near $9,300 while the Solo 401(k) allows roughly $32,800. At very high incomes both plans converge on the $70,000 cap. Solo 401(k)s also allow loans and Roth treatment — SEP-IRAs do not.