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.
Solo 401(k) advantage — the elective deferral component
Solo 401(k)'s key advantage over SEP IRA: the $23K elective deferral does NOT depend on income. Self-employed with $50K net earnings can contribute up to $23K elective + ~10K profit-sharing = $33K total. SEP IRA on same income: 25% × $50K = $12.5K maximum.
For lower-income self-employed (income <$200K), Solo 401(k) allows substantially higher contributions than SEP IRA. Only at very high income (~$300K+) where SEP's 25% × income reaches $69K cap does SEP catch up.
Additional features: Roth elective deferrals allowed (SEP IRA is traditional only); loan provisions allowed (SEP IRA has no loan provision); catch-up contributions structurally same.
For most self-employed individuals, Solo 401(k) is the optimal retirement plan choice. The main considerations: must have no full-time employees other than spouse; requires Form 5500-EZ annual filing when assets >$250K (simple but additional administrative step).
Mega backdoor Roth in Solo 401(k)
Advanced strategy: Solo 401(k) plans can be designed to allow after-tax contributions PLUS in-plan Roth conversions ('mega backdoor Roth'). Combined with elective deferral and employer contribution, this can effectively maximize tax-advantaged saving substantially beyond standard limits.
Mechanism: contribute up to $23K traditional or Roth elective + 25% of compensation as employer profit-sharing + additional after-tax contributions up to total cap ($69K-$76.5K). After-tax contributions can be immediately converted to Roth in-plan ('mega backdoor Roth'). All elements together — pre-tax + Roth + after-tax-to-Roth — can equal the full $69K cap.
Requirements: plan must permit after-tax contributions AND in-plan Roth conversions. Not all Solo 401(k) providers support this. Custom plan documents from providers like My Solo 401k Financial, Discount Solo 401k, or other specialty providers are typically required.
For very-high-income self-employed (300K+) wanting maximum tax-advantaged Roth saving, mega backdoor Roth in Solo 401(k) is unmatched. Standard providers (Fidelity, Schwab, Vanguard Solo 401(k)) typically don't support — must use specialty provider.
Solo 401(k) contribution scenarios (2024)
Reference Solo 401(k) contribution amounts at various self-employment income levels.
| Net self-employment income | Elective + employer max | Effective rate |
|---|---|---|
| $50K | $33K (incl. $23K elect.) | 66% |
| $75K | $41K | 55% |
| $100K | $48K | 48% |
| $150K | $58K | 39% |
| $200K | $69K cap | 35% |
| $300K+ | $69K cap | 23% and falling |
Net self-employment income above ~$200K hits the $69K combined cap. For income under $200K, Solo 401(k) allows higher percentage of income to be sheltered than SEP IRA. For income above $300K, Solo 401(k) and SEP IRA produce same $69K maximum — choose Solo 401(k) for Roth option, SEP IRA for simplicity.
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.
When is this calculator unreliable?
When self-employment income calculation is incorrect (self-employed compensation for retirement purposes is net earnings from self-employment after deduction for half of SE tax — typically about 92.35% of net business income, then × 20% for the contribution calculation). Also unreliable when not aware of mega backdoor Roth possibility in custom plans. For complex retirement planning, consult retirement plan specialist.
References & Authoritative Sources
- Internal Revenue Service (IRS) — One-Participant 401(k) Plans · consulted June 1, 2026 · Federal regulator on Solo 401(k)
- U.S. Small Business Administration (SBA) — Self-Employed Retirement Plans · consulted June 1, 2026 · SBA guidance on self-employed retirement
- Vanguard — Solo 401(k) — Individual 401(k) Plans · consulted June 1, 2026 · Industry data on Solo 401(k) options
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
Solo 401(k) growth uses compound interest with regular contributions. The calculator returns balance projection. Solo 401(k) (also called Individual 401(k), Solo-K) is U.S. retirement plan for self-employed individuals with no employees (or only spouse as employee). 2024 contribution limit: employee elective deferral $23,000 + $7,500 catch-up if 50+; employer contribution up to 25% of compensation; combined cap $69,000 ($76,500 if 50+). Allows Roth elective deferrals (unique among self-employed plans). RELIABILITY: Reliable for documented contributions. Less reliable when income calculation is uncertain (self-employed compensation calculations are complex; net earnings from self-employment differ from gross revenue) or when comparing to alternatives without considering plan administration cost (Solo 401(k) requires Form 5500-EZ when assets exceed $250K).
Updated