Retirement & benefits · 2026
Solo 401(k) Contribution Calculator
A Solo 401(k) lets you contribute twice: once as the employee and once as the employer. This calculates both halves from your Schedule C profit.
W-2 wages can reduce the remaining Social Security wage base used in Schedule SE.
The employee deferral limit is shared across all 401(k), 403(b), and similar plans.
- Employee deferral
- $24,500
- Employer profit-sharing (20%)
- $22,304
- Catch-up contribution
- $0.00
- Adjusted net earnings (contribution base)
- $111,522
- Advantage over a SEP IRA
- $24,500
Transparent method
How this calculator works
- Estimate adjusted net earnings after the deductible half of self-employment tax.
- Use the remaining employee deferral after contributions to another workplace plan.
- Add the sole-proprietor employer contribution, subject to the annual defined-contribution limit, then add any remaining age-based catch-up.
What the result does not include
- This version is for a sole proprietor with no eligible employees other than a spouse.
- Plan-document rules, Roth catch-up requirements, controlled-group rules, and partnership or S-Corp compensation formulas are outside scope.
Common questions
Why is the employer rate 20% and not 25%?
The statute says 25% of compensation, but for a sole proprietor "compensation" is net earnings after subtracting the contribution itself. Solving that circular definition gives 25% ÷ 1.25 = 20% of adjusted net earnings. Every correct calculator uses 20%; if you see one using 25% on Schedule C profit, it is overstating your limit.
Solo 401(k) or SEP IRA?
At the same profit a Solo 401(k) almost always allows more, because you get the employee deferral on top of the same employer percentage. The SEP wins only on simplicity — no Form 5500 filing once assets pass $250,000, and later setup deadlines.
When is the deadline?
Employee deferrals must be elected by December 31, 2026. Employer contributions can be made up to your tax filing deadline including extensions. The plan itself generally has to exist before year end.
What if I also contribute to a 401(k) at a day job?
Your employee deferral limit is shared across plans. Employer contributions use a separate per-employer calculation. Enter what you already deferred so this tool does not offer the same employee limit twice.