How to Use a Solo 401(k) Calculator

To use a Solo 401(k) Calculator, simply enter your business structure, filing year, age, and net income. It helps estimate how much money you can contribute to your 401(k) plan. Small business owners can save up to the maximum limit for both employees and employers, making a Solo 401(k) one of the most powerful tax-saving tools available.

Key Takeaways:

• Entrepreneurs can save up to $72,000 in a 401(k) this year, but the final total depends on your situation. A Solo 401(k) calculator can help you find your limit.

• Making pre-tax 401(k) contributions lowers your taxable income today while also saving for retirement tomorrow.

• Know your business’s deadlines! Missing a deadline could cost you valuable tax savings for the year.

Try our calculator to see your estimated Solo 401(k) contribution in seconds.

What is a Solo 401(k)?

A Solo 401(k) is a retirement plan built for self-employed people without employees. It can also be called an Individual 401(k), SoloK, One-Participant 401(k), and more. They all refer to the same powerful tool that helps entrepreneurs reduce their tax burden while saving for retirement.

A Solo 401(k) allows business owners to save money as both an employer and an employee. This lets you save much more each year compared to other retirement accounts like an IRA. And as a bonus, employer contributions are tax-deductible for your business.

How Does a Solo 401(k) Calculator Work?

A Solo 401(k) calculator estimates your maximum contribution based on:

1. Your company’s business structure

• Are you a sole proprietor, single-member LLC, S-Corp, C-Corp, or partnership? Each type is taxed differently.

2. Plan year contribution limits

• Limits are usually adjusted yearly by the IRS.

3. Age

• If you will be 50 or older by the end of the plan year, you can also make catch-up (50+) or super catch-up (60-63) contributions, which increase how much you can save.

4. Net earnings

• Your employer contribution limit is based on your earnings for the year. Higher earnings usually mean higher contribution limits.

The benefit of using a Solo 401(k) calculator is that it handles the math for you. You do not have to be a tax expert to get a clear picture of your contribution limit! Try ShareBuilder 401k’s Contribution Calculator to see just how simple it can be.

Learn how ShareBuilder 401k can support you and your business with a Solo 401(k).

How Much Can I Contribute to my Solo 401(k)?

The self-employed can save up to $72,000 in 2026 ($70,000 in 2025) to a Solo 401(k). Your exact limit depends on your business type, age, and earnings. A Solo 401(k) calculator helps with the heavy lifting to find your specific limit.

Here is a breakdown of contribution limits per business type for 2026:

*Exact employer contribution percentages depend on how much you pay in self-employment taxes.
Limits are set by the IRS and are subject to change annually. Check with your tax advisor for a final number.

Employee vs. Employer Contributions

Solo 401(k) contributions fall under two categories:

• Employee

  • Can be up to $24,500 in 2026 ($23,500 for 2025).

  • Can be made either as pre-tax (traditional) or after-tax (Roth).

  • If you are 50 or over, you can contribute an additional $8,000 as a catch-up contribution or $11,250 as a super catch-up contribution if you are ages 60-63.

• Employer (profit sharing)

  • The max limit is calculated as a percentage of your earnings, up to $47,500 in 2026.

  • Are only made pre-tax and are 100% tax deductible.

A Smart Approach to Solo 401(k) Saving

• Make automatic monthly employee contributions throughout the year.

• Before the tax filing deadline, examine your retirement saving goals.

• Use a Solo 401(k) calculator to see how much you can contribute.

• Make a one-time employer contribution.

This will help to prevent mistakes and spread savings throughout the year. Make sure to check with a tax advisor before making final decisions.

Solo 401(k) Contribution Deadlines

Contribution deadlines for a Solo 401(k) depend on how your business is structured. Employer contributions are generally due by:

• March 15th for S-Corps and Partnerships

• April 15th for Sole Proprietors and Single Member LLCs

See our Solo 401(k) Contribution Deadlines article for a full breakdown of employee and employer contribution and setup deadlines.

Solo 401(k) & Solo 401(k) Calculator FAQs

How accurate are Solo 401(k) calculators?

A Solo 401(k) calculator is a great starting point, but are only as accurate as the info you put in. Factors like changes in earnings or your business structure can affect the numbers it gives you. Always check with a tax advisor before making final decisions.

Who is a good fit for a Solo 401(k) plan?

A Solo 401(k) could be a good fit if you are a business owner or make decisions for a business with no employees. This includes solopreneurs, freelancers, contractors, sole proprietors, etc.

Who is covered under a Solo 401(k)?

A Solo 401(k) covers any owner or owners of a business and their spouses. If a spouse earns income from the business, they may also contribute to the plan. Rules can vary by provider, so check before starting a plan.

How can I start a Solo 401(k)?

You can start by getting an instant online quote today. You can speak with one of ShareBuilder 401k’s retirement experts to see if a Solo 401(k) is the right fit for you.

Can I still have a Solo 401(k) for business if I also have a day job?

Yes, you can contribute to both a Solo 401(k) and to a 401(k) account offered through your day job. But keep in mind that the employee deferral limit of $24,500 applies across all plans combined. Always check with a tax advisor before making final decisions.