Solo 401(k) Calculator 2025
Calculate your maximum contribution limits and tax savings
💎 Your Maximum Contribution
📖 Solo 401(k) Complete Guide
2025 Contribution Limits
- Employee Elective: $23,500 ($31,000 if 50+)
- Employer Profit Sharing: Up to 25% of W-2 wages (S-Corp) or 20% of self-employment income
- Total Annual Limit: $70,000 ($77,500 if 50+)
Key Advantages
- Highest contribution limits for self-employed
- Both employee and employer contributions
- Roth option available for employee deferrals
- Spouse can participate if employed by business
- Mega backdoor Roth potential
Business Structure Considerations
- Sole Proprietor/LLC: 20% of net self-employment income
- S-Corporation: 25% of W-2 wages (optimize salary vs distributions)
About This Calculator
Calculate maximum Solo 401(k) contributions for self-employed individuals with 2025 limits ($23,500 employee + $7,500 catch-up + 25% employer). Compares sole proprietor, S-Corp, LLC structures, includes spouse contributions, tax savings analysis, and SEP IRA/SIMPLE IRA comparison.
Frequently Asked Questions
What is the maximum Solo 401(k) contribution for 2025?
2025 maximum: $70,000 total ($77,500 if age 50+). Breakdown: Employee elective deferral $23,500 + Catch-up $7,500 (age 50+) + Employer profit-sharing up to 25% of compensation (S-Corp/LLC) or 20% of net self-employment income (sole proprietor). Example: 45-year-old sole proprietor earning $150k net can contribute $53,500 total ($23,500 employee + $30,000 employer @ 20%).
How does Solo 401(k) differ for sole proprietor vs S-Corp?
Sole proprietor: Employer contribution = 20% of net self-employment income (after deducting 1/2 SE tax). S-Corp: Employer contribution = 25% of W-2 wages (no SE tax). Key difference: S-Corp can contribute more at lower income levels. Example: $100k income鈥擲ole prop maxes $20k employer, S-Corp with $80k W-2 maxes $20k employer but saves $7,650 SE tax. S-Corp optimal for >$100k income with reasonable W-2 salary.
Should I choose Solo 401(k) or SEP IRA?
Solo 401(k) advantages: Higher contribution limits (2x employee + employer vs SEP employer-only), $23,500 employee deferral regardless of income (SEP limited to 25% of W-2 or 20% net SE income), Roth option, loan provisions ($50k), earlier access (age 59.5 vs 59.5 + still working). SEP IRA: Simpler administration, no annual filing (unless >$250k assets). Choose Solo 401(k) if: Income <$150k (employee deferral crucial), want Roth conversions, need loan access. Choose SEP IRA if: Income >$300k (same contribution, less complexity).
Can I contribute to Solo 401(k) if I have a W-2 job?
Yes, but employee elective deferral limit ($23,500) is shared across ALL 401(k) plans. Example: W-2 job contributes $15,000 to employer 401(k)鈥攜ou can only contribute $8,500 employee elective to Solo 401(k). However, employer profit-sharing contribution to Solo 401(k) is NOT affected (still up to 25%/20% of self-employment income). Strategy: Max W-2 employer 401(k) match first, then Solo 401(k) employer contribution, then remaining employee elective to Solo 401(k).
What are Solo 401(k) contribution deadlines for 2025?
Employee elective deferrals: Must be made by December 31, 2025 (cannot extend). Employer profit-sharing contributions: Due by business tax filing deadline鈥擜pril 15, 2026 for sole proprietors/LLCs (extendable to October 15, 2026), March 15, 2026 for S-Corps (extendable to September 15, 2026). Strategy: Wait to calculate employer contribution after year-end to optimize tax bracket/income, but set up automatic employee deferrals monthly to avoid cash flow crunch.
What are common Solo 401(k) mistakes that reduce contributions?
Top 5 costly mistakes: (1) Not separating employee/employer contributions鈥攃laiming only 20% total vs 20% employer + $23,500 employee = $20k vs $53k. (2) Forgetting catch-up at 50鈥攎issing $7,500/year = $112,500 over 15 years. (3) Using gross income for sole prop鈥攎ust deduct 1/2 SE tax first, reducing base by 7.65%. (4) Missing spouse contributions鈥攊f spouse has ANY self-employment income, can contribute full $70k separately. (5) Exceeding W-2 limitations鈥擲-Corp can only defer up to actual W-2 wages (can't defer $23,500 on $15k salary).
What are the total Solo 401(k) contribution limits for 2025?
In 2025, the total Solo 401(k) contribution limit is $70,000 ($77,500 if age 50+ with catch-up). This includes employee deferrals up to $23,500 ($31,000 with catch-up) plus employer profit-sharing contributions up to 25% of net self-employment income. For a sole proprietor earning $150,000 net, the employer portion is calculated on 92.35% of income after the self-employment tax deduction, allowing approximately $31,500 in employer contributions plus $23,500 employee deferral = $55,000 total. This makes Solo 401(k) one of the most powerful retirement savings vehicles for self-employed individuals.
Alex specializes in personal finance modeling with experience in investment analysis and tax optimization. He ensures every financial calculator follows current IRS guidelines and industry-standard formulas.
- CFA Level II Candidate
- B.S. in Finance, University of Michigan
- 8 years in financial planning tools