Solo K Calculator

Estimate your maximum Solo 401(k) retirement contributions as a self-employed individual or small business owner for 2024.

Calculate Your Max Contribution

Contribution Breakdown Table

Item	Amount
Net Self-Employment Income	$0.00
1/2 Self-Employment Tax	$0.00
Net Adjusted Income	$0.00
Max Employee Deferral (Solo)	$0.00
Max Employer Contribution (Solo)	$0.00
Total Max Solo 401k	$0.00

What is a Solo 401(k)?

A Solo 401(k), also known as an Individual 401(k) or Uni-k, is a retirement savings plan designed for self-employed individuals and small business owners who have no common-law employees (other than themselves and their spouse, if applicable). It offers the same benefits as a traditional 401(k) plan but is tailored for the owner-only business structure. This makes the Solo 401k Calculator a vital tool for these individuals.

You can contribute both as an “employee” (elective deferrals) and as an “employer” (profit-sharing contributions) to a Solo 401(k), allowing for potentially much higher contribution limits compared to SEP IRAs or SIMPLE IRAs, especially at lower income levels. Our Solo 401k Calculator helps you find these limits.

Who Should Use It?

• Sole proprietors (freelancers, consultants, independent contractors)
• Partners in a partnership
• S-corporation or C-corporation owners with no other full-time employees (excluding spouse)
• Individuals with side-gig income in addition to a W-2 job

Common Misconceptions

• It’s only for high earners: While high earners benefit greatly, even those with moderate self-employment income can contribute more than with other plans thanks to the employee deferral portion.
• It’s complicated to set up: Many financial institutions offer streamlined Solo 401(k) plans that are relatively easy to establish.
• You can’t have one if you have a W-2 job: You can contribute to a Solo 401(k) from your self-employment income even if you participate in a 401(k) at a W-2 job, though your employee deferral limit is shared between both. The Solo 401k Calculator accounts for this.

Solo 401(k) Contribution Formula and Mathematical Explanation

The maximum contribution to a Solo 401(k) for 2024 is determined by combining two parts, subject to overall IRS limits:

1. Employee Contribution (Elective Deferral): As an “employee,” you can defer up to $23,000 in 2024, or $30,500 if you are age 50 or older (including the $7,500 catch-up contribution). This limit is per person, across all 401(k) and 403(b) plans.
2. Employer Contribution (Profit Sharing): As the “employer,” you can contribute up to 25% of your net adjusted self-employment income. For sole proprietors, this is effectively 20% of net self-employment income *before* the 1/2 SE tax deduction, but calculated as 25% of net income *after* deducting one-half of your self-employment tax.
3. Overall Limit: The total combined employee and employer contributions cannot exceed $69,000 for 2024, or $76,500 if age 50 or older. This limit also includes any contributions made to other 401(k) plans if you have a W-2 job. The Solo 401k Calculator respects these limits.

Step-by-step Calculation:

1. Calculate Self-Employment Taxable Base: Net Income * 0.9235
2. Calculate Self-Employment Tax: SE Taxable Base * 0.153 (for the portion relevant to the deduction)
3. Calculate One-Half SE Tax Deduction: SE Tax / 2
4. Calculate Net Adjusted Self-Employment Income (Compensation): Net Income – One-Half SE Tax
5. Determine Max Employee Contribution: $23,000 (or $30,500 if 50+), reduced by any W-2 401(k) deferrals.
6. Calculate Max Employer Contribution: Net Adjusted Self-Employment Income * 0.25
7. Calculate Total Potential Contribution: Max Employee + Max Employer
8. Apply Overall Limit: The lesser of Total Potential Contribution or $69,000/$76,500 (reduced by W-2 contributions to other 401k-like plans from the total, although the employee part is directly reduced). The total Solo 401k contribution is limited to the overall annual limit minus any contributions made to other plans *by the same employer or related employers*, but for practical purposes with a W-2 job elsewhere, we reduce the employee limit and the overall limit available to the Solo 401k by the W-2 contributions.

Variables Table

Variable	Meaning	Unit	Typical Range
Net Income	Net profit from self-employment	$	0 – 1,000,000+
Age	Your age by year-end	Years	18 – 100
Existing Contributions	Employee deferrals to other 401k/403b	$	0 – 30,500+
1/2 SE Tax	Deductible portion of self-employment tax	$	Calculated
Net Adjusted Income	Compensation base for employer contribution	$	Calculated
Max Employee	Max elective deferral to Solo 401k	$	0 – 30,500
Max Employer	Max profit-sharing contribution	$	Calculated
Total Max	Total maximum Solo 401k contribution	$	0 – 76,500

Variables used in the Solo 401k Calculator

Practical Examples (Real-World Use Cases)

Example 1: Freelancer Under 50

Sarah, age 35, is a freelance graphic designer with a net self-employment income (Schedule C) of $80,000. She has no W-2 job.

• Age: 35
• Net Income: $80,000
• Existing W-2 Contributions: $0

Using the Solo 401k Calculator (or manual calculation):

1. 1/2 SE Tax ~ $5,652
2. Net Adjusted Income ~ $74,348
3. Max Employee Contribution: $23,000
4. Max Employer Contribution (25% of $74,348) ~ $18,587
5. Total Max Solo 401k: $23,000 + $18,587 = $41,587 (Well below $69,000 limit)

Sarah can contribute up to $41,587 to her Solo 401(k).

Example 2: Consultant Age 55 with W-2 Job

David, age 55, works part-time as a consultant (self-employed) with $150,000 net income. He also has a W-2 job where he contributed $10,000 to the 401(k) as an employee.

• Age: 55
• Net Income: $150,000
• Existing W-2 Contributions: $10,000

Using the Solo 401k Calculator:

1. 1/2 SE Tax ~ $10,597
2. Net Adjusted Income ~ $139,403
3. Overall Employee Limit (50+): $30,500
4. Available Employee for Solo 401k: $30,500 – $10,000 = $20,500
5. Max Employer Contribution (25% of $139,403) ~ $34,851
6. Total Potential Solo 401k: $20,500 + $34,851 = $55,351
7. Overall Limit (50+): $76,500. $55,351 + $10,000 (W2) = $65,351, which is less than $76,500.

David can contribute up to $55,351 to his Solo 401(k) ($20,500 employee + $34,851 employer).

How to Use This Solo 401k Calculator

1. Enter Your Age: Input your age as of the end of 2024 to see if you qualify for catch-up contributions.
2. Enter Net Self-Employment Income: This is your net profit from your business (e.g., Schedule C line 31) before deducting contributions to the Solo 401(k) or one-half of your self-employment taxes.
3. Enter Existing Contributions: If you also contribute to a 401(k) or 403(b) through a W-2 job, enter your employee deferrals here.
4. Click Calculate: The calculator will show your maximum total Solo 401(k) contribution, broken down into employee and employer parts, along with intermediate values like your net adjusted income.
5. Review Results: The primary result is your total max contribution. Intermediate results show the components. The chart and table provide a visual and tabular breakdown.
6. Decision-Making: Use the results to decide how much you want to contribute, up to the calculated maximum. You can choose to contribute less. Consider pre-tax vs. Roth contributions if your plan allows Roth.

The Solo 401k Calculator provides the maximums based on 2024 IRS rules. Consult with a financial advisor or tax professional to determine the best contribution strategy for your situation.

Key Factors That Affect Solo 401(k) Results

• Age: Individuals aged 50 and over can make additional catch-up contributions to the employee deferral portion.
• Net Self-Employment Income: The higher your net income, the higher your potential employer contribution, up to the overall limit. The Solo 401k Calculator reflects this.
• Contributions to Other Plans: If you participate in another 401(k) or 403(b) as a W-2 employee, your employee deferral limit for the Solo 401(k) is reduced by those contributions.
• Business Structure: While this calculator focuses on sole proprietorships/single-member LLCs for the 25% of adjusted net income rule, the general principles apply to partnerships and S-corps, though compensation is defined differently.
• Plan Document & Provider: Your specific Solo 401(k) plan document and provider might offer different features, such as Roth (after-tax) contributions or participant loans.
• Contribution Timing: Employee deferrals should generally be elected before year-end, while employer contributions can often be made up until the business tax filing deadline (including extensions).

Frequently Asked Questions (FAQ)

What is the maximum I can contribute to a Solo 401(k) in 2024?

For 2024, the total contribution limit is $69,000, or $76,500 if age 50 or over. This includes both employee and employer contributions. Use our Solo 401k Calculator to find your specific max based on income.

Can I contribute to both a Solo 401(k) and a SEP IRA?

You can have both, but contributions to both plans are subject to the overall defined contribution plan limits ($69,000/$76,500 in 2024) based on the same self-employment income. Usually, you would choose one or the other for a given year based on your goals.

Can I make Roth contributions to my Solo 401(k)?

Yes, if your Solo 401(k) plan document allows for Roth (after-tax) employee contributions. Employer contributions must be pre-tax, but some plans allow in-plan Roth conversions.

When is the deadline to set up and fund a Solo 401(k)?

To make employee deferrals for a given tax year, the plan generally must be established by December 31st of that year. Employer contributions can usually be made until the business’s tax filing deadline, including extensions.

What if I have no employees other than my spouse?

Your spouse can also participate in the Solo 401(k) if they earn legitimate income from the business, effectively doubling the potential family contribution if their income supports it.

How is the employer contribution calculated for an S-Corp owner?

For an S-Corp owner, the employer contribution is based on their W-2 wages from the S-Corp, not the K-1 distributions. The percentage is still up to 25% of W-2 compensation.

Is a Solo 401(k) better than a SEP IRA?

It depends. A Solo 401(k) often allows higher contributions at lower income levels due to the employee deferral, and may offer Roth options and loan provisions not available in SEPs. See our guide on Self-Employed Retirement Options.

What happens if I over-contribute to my Solo 401(k)?

Over-contributions need to be corrected by the tax filing deadline to avoid penalties. You should work with your plan administrator to remove the excess and any earnings.