Free Solo 401(k) contribution calculator for 2025. Calculate employee deferrals plus employer profit-sharing. Includes catch-up contributions and SEP IRA comparison.
The Solo 401(k) Contribution Calculator determines your maximum contribution as a self-employed individual with no employees (other than a spouse). Solo 401(k) plans combine employee salary deferrals with employer profit-sharing contributions, often allowing the highest total retirement savings of any plan type.
For 2025, you can defer up to $23,500 as an employee, plus contribute up to 25% of net self-employment earnings as employer profit-sharing, with a combined maximum of $70,000 ($77,500 with catch-up). This frequently exceeds SEP IRA limits at moderate income levels.
This calculator handles the self-employment tax adjustment and shows exactly how much you can save across both components. Self-employed individuals can contribute as both the employee and the employer, making the Solo 401(k) the most generous retirement plan available to single-owner businesses. For 2025, the combined limit can exceed $69,000 for those under 50, and even more with catch-up contributions. This ceiling helps you plan quarterly estimated tax payments accordingly.
The Solo 401(k) is often the best retirement plan for self-employed individuals because it allows both employee deferrals and employer contributions. This calculator shows you can save significantly more than a SEP IRA at most income levels, sometimes $10,000-$20,000 more per year. Knowing the exact split between employee and employer portions helps you maximize savings each year.
Employee Deferral = min($23,500 + catch-up, Net SE Income) Employer Profit-Sharing = min(Adjusted Net Earnings × 25%, $70,000 − Employee Deferral) Adjusted Net Earnings = Net SE Income − (SE Tax Deduction) Total = Employee + Employer (max $70,000, or $77,500 with catch-up)
Result: Employee: $31,000 | Employer: $27,871 | Total: $58,871
With $150,000 net SE income at age 52: employee deferral is $23,500 + $7,500 catch-up = $31,000. Adjusted net earnings yield 25% profit-sharing of $27,871. Total contribution: $58,871, versus only $27,871 in a SEP IRA at the same income.
The Solo 401(k)'s power comes from combining two contribution types. The employee deferral is a flat dollar amount available regardless of income (as long as earnings are sufficient). The employer profit-sharing scales with income. This dual structure means high contributions even at moderate incomes.
Self-employed individuals must reduce their net earnings by the deductible half of self-employment tax before calculating the 25% employer contribution. This is the same adjustment as with a SEP IRA. The effective employer contribution rate is approximately 20% of gross net SE income.
Choose a Solo 401(k) over a SEP IRA if: (1) your income is under $300,000 and you want to maximize savings, (2) you want a Roth option, (3) you want to borrow from the plan (loan feature), or (4) a spouse works in the business. Choose a SEP if simplicity is the top priority and you're at very high income where both hit the cap.
Employee deferral: $23,500. Catch-up (50+): additional $7,500 ($11,250 for ages 60-63). Employer profit-sharing: 25% of adjusted net earnings. Total limit: $70,000 (or $77,500/$81,250 with catch-up). These are the highest limits available for self-employed retirement plans.
For most self-employed individuals earning under $300,000, the Solo 401(k) allows more because it includes the $23,500 employee deferral on top of the employer profit-sharing. A SEP IRA only has the employer contribution (25% of adjusted earnings). The advantage is greatest at lower incomes.
Yes. Most Solo 401(k) providers now offer a Roth designated deferral option. The employee deferral portion ($23,500 + catch-up) can be designated as Roth. The employer profit-sharing portion must remain pre-tax but can be converted to a Roth account within the plan.
Any self-employed individual or business owner with no full-time employees other than a spouse. This includes sole proprietors, independent contractors, single-member LLCs, and partnerships with only spouse partners. Once you hire a non-spouse employee, the Solo 401(k) must be converted to a standard 401(k).
If plan assets are under $250,000, no annual filing is required. Once assets exceed $250,000 at year-end, you must file Form 5500-EZ with the IRS annually. This is still much simpler than a standard 401(k) plan.
If your spouse works in the business and receives compensation, they can make their own employee deferrals (up to $23,500 + catch-up) and receive employer profit-sharing. This can effectively double the household's total contribution from one business.