Introduction to Solo 401(k) employee and employer contributions
A Solo 401(k), also called an individual 401(k), lets an eligible self-employed owner contribute in two roles. The employee role can make an elective deferral, while the employer role can make a profit-sharing contribution. This calculator combines those layers so you can estimate the employee amount, employer amount, total contribution, and unused headroom under the 2024 limits programmed into the page.
The distinction between the two roles is important. Employee deferrals are governed by a personal annual limit shared with certain other workplace plans. Employer contributions instead depend on eligible compensation and business structure. A large headline plan limit therefore does not guarantee that every owner can contribute that amount. Income, age, entity type, and contributions made through another employer can all change the practical answer.
This is a planning calculator rather than a tax-return worksheet. It uses a simplified self-employment tax adjustment for a sole proprietor and assumes the corporate income entry represents W-2 wages. The result can help you compare scenarios, but final contributions should be checked against current IRS guidance, the plan document, payroll records, and filing deadlines.
How to use the Solo 401(k) income, age, and entity fields
Enter annual net self-employment income if you operate as a sole proprietor or single-member LLC taxed as a disregarded entity. Do not enter gross receipts before expenses. For the corporate option, enter the W-2 wage compensation being modeled; shareholder distributions, dividends, and owner draws are not treated as wages by this simplified calculation.
Next, enter your age for the contribution year and select the business type. Age determines whether this calculator adds its catch-up contribution. The entity selection determines whether the employer calculation uses the sole-proprietor percentage or the corporate wage percentage. Select Calculate to display the estimate. The Copy Result control appears after a valid calculation so you can retain the scenario in your planning notes.
- Use dollars per year for income and a whole number of years for age.
- Select the structure that matches how the business reports owner compensation.
- Review each result component, not only the combined total.
- Subtract employee deferrals made to another 401(k) or 403(b) when applicable.
If your year-end income is uncertain, run conservative and optimistic versions. Comparing several plausible income figures is usually more useful than assuming one forecast is exact.
The Solo 401(k) formulas and 2024 limits used here
The calculator first establishes a compensation base. For the sole-proprietor path, it approximates self-employment tax as income multiplied by 92.35% and then by 15.3%. Half of that estimated tax is removed from income. The corporate path does not apply that adjustment because the entered figure is treated as W-2 wages.
The employee portion follows the 2024 elective-deferral amount. An individual can defer up to dollars, and a participant age 50 or older can receive an additional dollars in this model. The original formula is:
The employee deferral is also limited by available compensation. The employer calculation then applies 20% to the adjusted sole-proprietor base or 25% to corporate wages:
Finally, the calculator checks the combined amount against both its annual plan limit and available compensation. It uses dollars as the 2024 base total limit and dollars when its age-50 catch-up applies. A result may therefore stop growing because the employee ceiling, compensation, or combined plan ceiling has been reached.
Contribution limits by age in this calculator
| Age |
Employee deferral limit |
Displayed combined limit |
| Under 50 |
$23,000 |
$66,000 |
| 50 or older |
$30,500 |
$73,500 |
Worked example: $60,000 of sole-proprietor income
Consider a 45-year-old owner who enters $60,000 of net self-employment income and chooses the sole-proprietor option. The calculator estimates self-employment tax, removes half of that estimate, and produces a compensation base of about $55,761. Because this base exceeds the $23,000 employee ceiling, the employee deferral reaches $23,000.
The employer side is 20% of the adjusted base, or approximately $11,152. The displayed total is therefore about $34,152. The remaining headroom is not an extra guaranteed contribution; it shows the difference between the calculated total and the lower of the compensation-based ceiling or the annual total limit. Increasing income in another run will generally raise the employer portion while the employee portion remains at its ceiling.
For another illustration, suppose a 45-year-old consultant has dollars of income. In a simplified example before the calculator’s self-employment tax adjustment, the employee role could use the lesser of dollars or compensation. A rough employer calculation at would be dollars, producing dollars before finer adjustments. That remains below the modeled dollar ceiling.
At dollars of income, a theoretical 20% employer amount would be dollars, but the combined dollar limit would constrain the result. In this calculator, a participant age 50 or older can have an employee amount of dollars and a displayed combined limit of dollars.
How to interpret employee deferral, employer share, and headroom
The employee deferral shows the amount attributed to the owner’s employee role. If that value has reached its ceiling, more income will not increase it. The employer contribution shows the profit-sharing amount generated by the eligible compensation base and selected entity rate. That figure can continue rising after the employee amount is capped, until compensation or the total plan limit becomes binding.
The total contribution is the sum permitted by this calculator after its caps are applied. Remaining headroom is the difference between that total and the calculator’s applicable maximum. It should not be read as an instruction to contribute immediately. Cash flow, deductions, payroll, another retirement plan, and the plan document can reduce the amount actually available.
A useful reasonableness check is direction. Higher eligible compensation should generally increase the employer contribution. Choosing the corporate option applies 25% to the entered wage amount and removes the sole-proprietor tax adjustment. Entering age 50 or above adds the catch-up amount. If a result does not follow those patterns, recheck whether income was entered as net profit or wages and whether the correct entity was selected.
Limitations of this Solo 401(k) planning estimate
This page deliberately simplifies several rules. The sole-proprietor calculation approximates self-employment tax rather than reproducing a complete tax return, wage-base interaction, or self-employed contribution worksheet. The corporate path assumes the amount entered is valid W-2 compensation. It does not test ownership, employee eligibility, controlled-group rules, earned-income definitions, plan-document restrictions, or contribution deadlines.
The employee limit may be shared across plans. Someone who already deferred through a day-job 401(k) or 403(b) cannot normally claim a second full employee limit merely because a separate business sponsors a Solo 401(k). Employer contributions may still be possible based on eligible business compensation, but that coordination is outside the form.
Plan administration matters as well. Employee deferrals and employer contributions may have different election or funding deadlines. Plans with sufficient assets can have filing duties, including Form 5500-EZ requirements. Roth treatment, after-tax contributions, cash-balance plans, and advanced conversion strategies are also beyond this calculator’s standard pre-tax model.
Contribution capacity is not the same as affordability. A business can report accounting profit without having enough cash to fund the maximum. For perspective, repeated saving can compound substantially: the original page illustrated a dollar annual contribution growing at an assumed 7% over 20 years. Investment returns are uncertain, however, and that illustration is not a forecast or part of the calculator result.
Use the output to frame a conversation and compare scenarios. Confirm the final amount with current IRS limits, bookkeeping records, payroll reports, the plan provider, and a qualified tax professional before making or deducting a contribution.
Related retirement planning calculators
After testing a Solo 401(k) scenario, compare it with the 401(k) employer match calculator, use the Solo 401(k) contribution split planner to consider funding roles, or review borrowing costs with the 401(k) loan repayment calculator.
Enter net self-employment income, age, and business type to estimate the Solo 401(k) employee deferral, employer contribution, total contribution, and remaining headroom under this calculator’s 2024 limits.