401(k), IRA & Roth
A solo 401(k) calculator for the self-employed clients you want
A solo 401(k) calculator: sole proprietors see how employee deferrals and employer profit-sharing combine, up to $72,0002026 · IRS for 2026, and how the account could grow.
Included on every plan, even the free Practitioner plan. No card needed.
How much can I contribute to a solo 401(k) in 2026?
Two parts: an employee deferral of up to $24,5002026 · IRS, and an employer profit-sharing contribution of up to 20% of net self-employment income after the deductible half of self-employment tax. Together they cannot exceed $72,0002026 · IRS, excluding catch-up contributions, or the client's net earnings.
November and December, while there's time to open a plan
A profitable year makes freelancers and consultants look for deductions in the fourth quarter. A solo 401(k) is often the biggest one available, but opening one has deadlines and the contribution math is confusing. They search for the number before deciding whether it's worth the paperwork.
What the client types into a search box
“how much can I put in a solo 401k as a freelancer”
How a client works through it
Enter net self-employment income
Schedule C profit, the base for the employer contribution.
Enter the employee contribution
Up to the employee deferral limit.
Set employer profit-sharing
A percentage of income, effectively capped at 20% for sole proprietors.
Project the balance
Return, income growth and years to retirement give the projected account.
What lands in your inbox
When a client asks your firm to review the result, the request arrives as a contact record with their inputs and results attached, by email and, on paid plans, by webhook to your CRM.
Received
Net self-employment income tells you the size of the deduction opportunity. Incomes where the employer contribution is large suggest a client who may also benefit from an S corporation analysis. A current balance of zero means a plan to open, which has a deadline.
Why is the employer contribution capped at 20%?
For a sole proprietor, the plan's 25% employer rate works out to 20% of net self-employment income after the deductible half of self-employment tax, because the contribution reduces the income it is based on. Employer Profit-Sharing reflects that.
First-Year Contribution is the most useful figure for tax planning: it is the deduction available this year. Balance at Retirement shows the long-term value.
Results shown: Balance at Retirement · Employee Contributions · Employer Profit-Sharing · Investment Growth · First-Year Contribution.
Why is a solo 401(k) calculator a CPA firm's best year-end tool?
It shows the self-employed client a large, immediate tax saving and makes the case for professional help in one screen. The contribution math depends on net self-employment income, which only an accurate Schedule C gives, so the request leads naturally to bookkeeping, tax projection and plan setup.
Advisers benefit too: a solo 401(k) needs investing, and a new plan is a new account.
Follow-ups this request opens
- Open a solo 401(k) before the plan-establishment deadline
- Calculate the exact employer contribution from the final Schedule C
- Compare solo 401(k), SEP IRA and S corporation wage strategies
- Choose Roth or pre-tax for the employee deferral
What this calculator leaves out
- Models a sole proprietor; S corporation owners contribute based on W-2 wages instead.
- Age 50+ catch-up contributions are not included.
- 2026 limits are held flat in future years.
- Does not model the tax saving itself.
Platform disclaimer shown under the calculator: Estimates only. Models a sole proprietor: the employer contribution is a percentage of net SE income after the deductible half of self-employment tax (max 20%). Applies the 2026 IRS limits — $24,500 employee deferral and $72,000 total — held flat in future years; age 50+ catch-up contributions are not included. Assumes constant return and income. Confirm plan rules with your administrator or tax professional.
Compliance note for firms
Plan design and contribution amounts are tax advice. Under Circular 230 §10.37, recommending a contribution needs the final net earnings figure and consideration of other plans or employees. A solo 401(k) is only for owners with no eligible employees, which the calculator doesn't check.
Not legal advice. See our disclaimer and the guide to compliance for client calculators.
2026 figures this page relies on
| Figure | Value | Tax year | Source |
|---|---|---|---|
| 401(k)/403(b)/457(b) employee deferral limit | $24,500 | 2026 | IRS |
| Solo 401(k) combined employee + employer limit (excl. catch-up) | $72,000 | 2026 | IRS |
| Self-employment tax rate and base | 15.3% (12.4% Social Security + 2.9% Medicare) on 92.35% of net profit | 2026 | IRS |
The same values drive the calculator. Full list on the 2026 figures page.
Terms your client sees in the calculator
These definitions appear in the calculator's collapsible Definitions block, so clients don't have to call to ask what a label means.
- Solo 401(k)
- A 401(k) plan for a self-employed person with no employees other than a spouse. Because you are both employer and employee, you can contribute in both roles: an employee salary deferral plus an employer profit-sharing contribution. This calculator models a sole proprietor and combines the two into a single projected balance.
- Employee deferral
- The portion you contribute in your role as employee. The limit is $24,500 for 2026 (IRS), and it cannot exceed your net earnings from self-employment. The calculator holds this limit flat in future years rather than projecting inflation adjustments, and it does not add age 50+ catch-up contributions.
- Employer profit-sharing contribution
- The portion your business contributes as employer, figured as a percentage of net self-employment income after the deductible half of self-employment tax. The plan’s 25% rate works out to an effective maximum of 20% for a sole proprietor (IRS rules, as applied here for 2026), because the contribution itself reduces the income it is based on.
- Total contribution limit
- The cap on employee deferrals and employer contributions combined: $72,000 for 2026 (IRS), not counting catch-up contributions. The calculator applies it each year, trimming the employer portion if the two together would exceed it, and holds the figure flat in future years. At higher incomes this cap, not the percentage, is what limits contributions.
- Net self-employment income
- Your business revenue minus business expenses, as reported on your Schedule C for a sole proprietor. It is the starting point for the employer contribution. The calculator reduces it by the deductible half of self-employment tax before applying your profit-sharing percentage, and grows it each year at the income growth rate you enter.
- Deductible half of self-employment tax
- Self-employed people pay both the employee and employer shares of Social Security and Medicare tax, and may deduct the employer-equivalent half. For a Solo 401(k), that deduction is subtracted from net self-employment income before the employer contribution percentage is applied, which is one reason the effective employer rate is lower than the plan rate.
In our glossary: Elective deferral · Self-employment tax
Solo 401(k) calculator: questions from firms and clients
What is the total solo 401(k) limit for 2026?
$72,0002026 · IRS, combining employee and employer contributions, excluding catch-up contributions.
Who can have a solo 401(k)?
Self-employed people and business owners with no eligible employees other than a spouse.
Why is the employer contribution 20%, not 25%?
For sole proprietors, the contribution reduces the income it's figured on, which makes the effective rate 20% of net SE income after the deductible half of SE tax.
Can S corporation owners use this?
The math differs: contributions are based on W-2 wages. The firm should run that version.
Is there a deadline?
Plans generally must be established by the end of the year for employee deferrals; employer contributions can often be made until the filing deadline. Confirm the current rules with the firm.
Solo 401(k) or SEP IRA?
A solo 401(k) usually allows more at modest incomes because of the employee deferral. A SEP is simpler. The firm can compare both.
Can the deferral be Roth?
Many plans allow Roth employee deferrals.
Which plan includes it?
Every plan, including the free Practitioner plan, which runs up to 5 calculators at once alongside the other retirement tools. Firm (up to 50) and Network (no cap) add webhooks and white-label. See pricing.
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