Solo 401(k) Calculator: Project a Self-Employed Retirement Balance
Project how a Solo 401(k) could grow — the retirement plan for self-employed earners with no employees, designed to let owner-operators save aggressively in good years.
Adjust the inputs and select Calculate for a full breakdown.
Year-by-year growth schedule
Compare Common Scenarios
How the numbers shift across typical situations for this calculator:
| Scenario | Future value | Total contributions | Total interest earned |
|---|---|---|---|
| $40k · $1.5k/mo · 7% · 20yr | $942,939.54 | $400,000.00 | $542,939.54 |
| $0 · $2k/mo · 8% · 25yr | $1,902,052.79 | $600,000.00 | $1,302,052.79 |
| $150k · $3k/mo · 6% · 15yr | $1,240,570.17 | $690,000.00 | $550,570.17 |
| $10k · $500/mo · 7% · 30yr | $691,150.47 | $190,000.00 | $501,150.47 |
How This Calculator Works
Enter the current Solo 401(k) balance, the return you expect, the years until retirement, and the monthly contribution that combines your employee deferral and any employer profit-sharing. The calculator compounds monthly and shows the projected balance plus the share built by investment growth.
The Formula
Future Value with Regular Contributions
P = starting amount, PMT = monthly contribution, r = monthly rate (annual ÷ 12), n = number of months
Worked Example
With $40,000 saved, $1,500 added monthly, and a 7% average return over 20 years, a Solo 401(k) reaches about $942,900. Contributions account for $400,000 of that; investment growth supplies the remaining $543,000.
Key Insight
The Solo 401(k)'s structural advantage is the dual contribution: you contribute as the employee and again as the employer of your own business. Combined, the cap is far above what a SEP IRA, traditional IRA, or workplace 401(k) allows — useful when a strong year leaves room to shelter income.
Frequently Asked Questions
Who can open a Solo 401(k)?
Self-employed earners with no employees other than a spouse. Once you hire a non-spouse employee, the Solo 401(k) usually has to convert to a standard 401(k) plan.
How much can I contribute?
Both employee deferral and an employer profit-sharing share are allowed, up to a combined IRS cap that is much higher than a regular 401(k) deferral on its own. Limits change yearly — check the current IRS figures.
Solo 401(k) or SEP IRA?
Solo 401(k)s often allow a higher contribution at lower incomes thanks to the dual structure, and permit loans. SEP IRAs are simpler to run. Choice depends on income level and how active you want the account to be.
Is there a Roth Solo 401(k)?
Yes. Many plans offer a Roth bucket for the employee-deferral portion. Employer profit-sharing contributions are typically pre-tax only.
Can I borrow from a Solo 401(k)?
Most plans allow a participant loan — up to half the balance, capped at $50,000. The loan is repaid with interest to your own account; missed payments can be treated as a distribution.
Related Calculators
Data Sources & Benchmarks
This calculator draws on 3 independent, dated sources. The starting values for expected annual return are taken from the benchmarks below and refresh whenever the snapshots are updated.
Methodology & Review
The projection compounds the balance monthly at a constant expected return and adds a fixed monthly contribution. It assumes contributions stay within the Solo 401(k) limit (combined employee and employer-side caps) and excludes fees and tax.
Written by Ugo Candido · Last updated May 17, 2026.