Free Solo 401(k) contribution calculator for 2026. Estimate employee deferrals, self-employed employer contributions, catch-up amounts, and the SEP IRA comparison.
The Solo 401(k) Contribution Calculator estimates your maximum contribution as a self-employed individual with no eligible employees other than a spouse. Solo 401(k) plans combine employee salary deferrals with employer profit-sharing contributions, which often makes them one of the highest-capacity retirement plans available to a single-owner business.
For 2026, the employee deferral limit is $24,500, with an $8,000 catch-up for most participants age 50 or older and an $11,250 catch-up for ages 60-63. The combined annual-additions limit is $72,000 before catch-up contributions, or up to $80,000 / $83,250 depending on the catch-up tier. For self-employed owners, the employer contribution is based on adjusted earnings after the deductible half of self-employment tax.
This calculator handles that self-employment tax adjustment, shows the split between employee and employer contributions, and compares the result with a SEP IRA so you can see which plan gives more room at your income level.
A Solo 401(k) often allows more retirement savings than a SEP IRA because it stacks the employee deferral on top of the employer contribution. This worksheet helps you see the current-year contribution ceiling, how the self-employment adjustment changes the employer amount, and whether the extra complexity is worthwhile for your business.
Employee Deferral = min($24,500 + catch-up, Net SE Income) Employer Contribution = min(Adjusted Net Earnings × 20%, Combined Limit − Employee Deferral) Adjusted Net Earnings = Net SE Income − Deductible Half of SE Tax Total = Employee Deferral + Employer Contribution
Result: Employee: $32,500 | Employer: $27,881 | Total: $60,381
With $150,000 of net self-employment income at age 52, the employee deferral is $24,500 plus the $8,000 catch-up. After the self-employment tax adjustment, the employer contribution is about $27,881 using the 20% self-employed equivalent rate. Total Solo 401(k) contribution is about $60,381, versus about $27,881 for a SEP IRA at the same income.
A Solo 401(k) combines two contribution channels: the employee deferral and the employer contribution. That lets owner-only businesses save more than a SEP IRA at many income levels because a SEP IRA only has the employer contribution layer.
The employer side is not based on raw Schedule C profit. Self-employed owners first reduce earnings by the deductible half of self-employment tax, then apply the self-employed equivalent contribution rate. That is why this worksheet uses an adjusted-earnings step before calculating the employer amount.
If your income is relatively modest for a small business owner, the Solo 401(k) usually wins on contribution room. If simplicity is more important than maximum savings, a SEP IRA may still be attractive. Comparing both on the same page makes it easier to see whether the extra paperwork is justified.
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This worksheet estimates the employee-deferral and employer components separately, then applies the current IRS annual-limit rules and the self-employment-tax adjustment. For self-employed owners, the employer contribution uses the 20% equivalent rate on adjusted net earnings. It is a planning aid, not a payroll or tax filing calculation.
The 2026 employee deferral limit is $24,500. The standard catch-up is $8,000 for most participants age 50 or older, and the ages 60-63 super catch-up is $11,250. The combined annual-additions limit is $72,000 before catch-up contributions, or up to $80,000 / $83,250 depending on the catch-up tier.
For self-employed owners, the employer contribution is calculated on adjusted earnings after the deductible half of self-employment tax. That produces an effective 20% equivalent rate in the worksheet, even though many summaries quote a 25% compensation formula for non-owner employees.
For many self-employed people under roughly the low-to-mid six figures, the Solo 401(k) allows more because it adds the employee deferral on top of the employer contribution. A SEP IRA only has the employer piece, so the Solo 401(k) usually pulls ahead until both plans approach the combined cap.
If your spouse works in the business and receives compensation, they can generally make their own employee deferral and receive an employer contribution as well. That can substantially increase the household total from the same business.
Many providers offer a Roth designated account for the employee-deferral portion. Employer contributions are still tracked separately under the plan and may have different tax treatment depending on plan design and current law.