{
  "id": "solo-401k",
  "version": "623d05e402f5",
  "status": "published",
  "name": "Solo 401k Calculator",
  "question": "How much can I put in a solo 401(k)?",
  "summary": "Works out the most a self-employed person can put into a solo 401(k) for 2026: elective deferrals, catch-up and the employer contribution, from net profit by the IRS worksheet for the self-employed.",
  "category": "finance",
  "subcategory": "retirement",
  "url": "https://www.acalculator.org/finance/solo-401k-calculator",
  "markdown": "https://www.acalculator.org/finance/solo-401k-calculator.md",
  "kind": "function",
  "method": "Self-employment tax = 12.4% × the smaller of 92.35% of profit and ($184,500 − job wages) + 2.9% × 92.35% of profit (none under $400 of net earnings). Net earnings = profit − half of that tax. Employer part = the smallest of net earnings × rate ÷ (1 + rate), $360,000 × rate, $72,000 − deferrals, and (net earnings − deferrals) ÷ 2, where deferrals = the smaller of ($24,500 − deferrals to other plans) and net earnings. Catch-up = the smaller of the age catch-up ($8,000; $11,250 at 60 to 63) and net earnings − employer part − deferrals. Total = employer part + deferrals + catch-up.",
  "assumptions": [
    "Tax year 2026 (IRS Notice 2025-67); a sole proprietor or partner with no employees other than a spouse. For an S corporation owner, the employer part is figured on W-2 wages instead.",
    "Deferrals are made to the full limit before the employer part; Roth deferrals count the same toward the limits.",
    "Catch-up contributions to other plans are not included. An estimate, not tax advice."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "profit": {
        "title": "Net self-employment profit",
        "description": "Your 2026 net profit from the business (Schedule C line 31), or your share of partnership self-employment earnings.",
        "type": "number",
        "x-unit": "USD",
        "minimum": 0,
        "maximum": 1000000000
      },
      "age": {
        "title": "Your age at the end of 2026",
        "description": "Catch-up contributions start at 50; ages 60 to 63 get a larger catch-up.",
        "type": "string",
        "enum": [
          "under50",
          "50",
          "60"
        ]
      },
      "rate": {
        "title": "Employer contribution rate",
        "description": "The plan’s employer (profit-sharing) rate, up to 25%.",
        "type": "number",
        "x-unit": "percent",
        "minimum": 0,
        "maximum": 25
      },
      "other": {
        "title": "Deferrals to other 401(k) plans (optional)",
        "description": "Elective deferrals you make in 2026 to another employer’s 401(k), 403(b) or similar plan; they share the limit.",
        "type": "number",
        "x-unit": "USD",
        "minimum": 0,
        "maximum": 1000000000
      },
      "w2": {
        "title": "Social Security wages from a job (optional)",
        "description": "W-2 Social Security wages from another job in 2026; they use up part of the Social Security wage base.",
        "type": "number",
        "x-unit": "USD",
        "minimum": 0,
        "maximum": 1000000000
      }
    }
  },
  "outputs": {
    "total": {
      "label": "Most you can contribute",
      "description": "Employer contribution + elective deferrals + catch-up (Publication 560 worksheet step 19).",
      "format": "money"
    },
    "employer": {
      "label": "Employer contribution",
      "description": "The smallest of net earnings × reduced rate, $360,000 × rate, $72,000 − deferrals and half of (net earnings − deferrals).",
      "format": "money"
    },
    "deferral": {
      "label": "Elective deferrals",
      "description": "$24,500 less deferrals to other plans, but no more than what net earnings leave.",
      "format": "money"
    },
    "catchUp": {
      "label": "Catch-up contributions",
      "description": "$8,000 at 50 or older, $11,250 at 60 to 63, but no more than what net earnings leave.",
      "format": "money"
    },
    "netEarnings": {
      "label": "Net earnings from self-employment",
      "description": "Net profit − the deduction for half of self-employment tax (worksheet step 3).",
      "format": "money"
    },
    "seTax": {
      "label": "Self-employment tax",
      "description": "Schedule SE: 12.4% of 92.35% of profit up to the wage base + 2.9% of 92.35% of profit.",
      "format": "money"
    },
    "seDeduction": {
      "label": "Deduction for half of self-employment tax",
      "description": "Half of the self-employment tax (worksheet step 2).",
      "format": "money"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "profit": 100000,
      "age": "under50",
      "rate": 25
    },
    "outputs": {
      "total": 43087.045,
      "employer": 18587.045,
      "deferral": 24500,
      "catchUp": 0,
      "netEarnings": 92935.225,
      "seTax": 14129.55,
      "seDeduction": 7064.775
    },
    "text": "With $100,000.00 of net profit, you can put up to $43,087.05 into a solo 401(k) for 2026."
  },
  "examples": [
    {
      "given": {
        "profit": 100000,
        "age": "under50",
        "rate": 25
      },
      "expect": {
        "seTax": 14129.55,
        "seDeduction": 7064.775,
        "netEarnings": 92935.225,
        "employer": 18587.045,
        "deferral": 24500,
        "catchUp": 0,
        "total": 43087.045
      },
      "source": "IRS Publication 560 (2025), chapter 5, Deduction Worksheet for Self-Employed (steps 1 to 21) and Rate Worksheet (rate ÷ (1 + rate)), with the 2026 amounts, https://www.irs.gov/publications/p560; IRS Notice 2025-67 (IRB 2025-49): 2026 limits $24,500 (402(g)), $8,000 catch-up, $11,250 at ages 60 to 63, $72,000 (415(c)), $360,000 (401(a)(17)), https://www.irs.gov/irb/2025-49_IRB; Schedule SE (Form 1040): 92.35% of net profit, 12.4% up to the $184,500 wage base and 2.9%, half deducted; hand calculation in content.mdx; Python 3 check in docs/progress/WP-128/xcheck.py"
    },
    {
      "given": {
        "profit": 100000,
        "age": "60",
        "rate": 25
      },
      "expect": {
        "employer": 18587.045,
        "deferral": 24500,
        "catchUp": 11250,
        "total": 54337.045
      },
      "source": "IRS Publication 560 (2025), chapter 5, Deduction Worksheet for Self-Employed (steps 1 to 21) and Rate Worksheet (rate ÷ (1 + rate)), with the 2026 amounts, https://www.irs.gov/publications/p560; IRS Notice 2025-67 (IRB 2025-49): 2026 limits $24,500 (402(g)), $8,000 catch-up, $11,250 at ages 60 to 63, $72,000 (415(c)), $360,000 (401(a)(17)), https://www.irs.gov/irb/2025-49_IRB; Python 3 check in docs/progress/WP-128/xcheck.py"
    },
    {
      "given": {
        "profit": 400000,
        "age": "50",
        "rate": 25
      },
      "expect": {
        "employer": 47500,
        "deferral": 24500,
        "catchUp": 8000,
        "total": 80000
      },
      "source": "IRS Publication 560 (2025), chapter 5, Deduction Worksheet for Self-Employed (steps 1 to 21) and Rate Worksheet (rate ÷ (1 + rate)), with the 2026 amounts, https://www.irs.gov/publications/p560 (step 10: $72,000 − deferrals); IRS Notice 2025-67 (IRB 2025-49): 2026 limits $24,500 (402(g)), $8,000 catch-up, $11,250 at ages 60 to 63, $72,000 (415(c)), $360,000 (401(a)(17)), https://www.irs.gov/irb/2025-49_IRB; Schedule SE (Form 1040): 92.35% of net profit, 12.4% up to the $184,500 wage base and 2.9%, half deducted; Python 3 check in docs/progress/WP-128/xcheck.py"
    },
    {
      "given": {
        "profit": 30000,
        "age": "under50",
        "rate": 25
      },
      "expect": {
        "netEarnings": 27880.5675,
        "deferral": 24500,
        "employer": 1690.28375,
        "total": 26190.28375
      },
      "source": "IRS Publication 560 (2025), chapter 5, Deduction Worksheet for Self-Employed (steps 1 to 21) and Rate Worksheet (rate ÷ (1 + rate)), with the 2026 amounts, https://www.irs.gov/publications/p560 (step 12: one-half of net earnings less deferrals); Python 3 check in docs/progress/WP-128/xcheck.py"
    },
    {
      "given": {
        "profit": 100000,
        "age": "under50",
        "rate": 25,
        "other": 10000,
        "w2": 180000
      },
      "expect": {
        "seTax": 3236.15,
        "seDeduction": 1618.075,
        "deferral": 14500,
        "employer": 19676.385,
        "total": 34176.385
      },
      "source": "IRS Publication 560 (2025), chapter 5, Deduction Worksheet for Self-Employed (steps 1 to 21) and Rate Worksheet (rate ÷ (1 + rate)), with the 2026 amounts, https://www.irs.gov/publications/p560; IRS Notice 2025-67 (IRB 2025-49): 2026 limits $24,500 (402(g)), $8,000 catch-up, $11,250 at ages 60 to 63, $72,000 (415(c)), $360,000 (401(a)(17)), https://www.irs.gov/irb/2025-49_IRB (deferrals to all plans share the limit); Schedule SE (Form 1040): 92.35% of net profit, 12.4% up to the $184,500 wage base and 2.9%, half deducted (line 8a W-2 wages); Python 3 check in docs/progress/WP-128/xcheck.py"
    }
  ],
  "sources": [
    "IRS, Publication 560 (2025), Retirement Plans for Small Business: chapter 5, Deduction Worksheet for Self-Employed, steps 1 to 21, and the Rate Worksheet for Self-Employed (rate ÷ (1 + rate)); What’s New gives the 2026 limits ($24,500 elective deferrals, $8,000 catch-up, $11,250 at ages 60 to 63). https://www.irs.gov/publications/p560 (retrieved 2026-10-18)",
    "IRS, Notice 2025-67 (Internal Revenue Bulletin 2025-49), 2026 amounts relating to retirement plans: section 415(c)(1)(A) limit $72,000; section 402(g)(1) $24,500; section 414(v) catch-up $8,000 and $11,250 for ages 60 to 63; section 401(a)(17) compensation $360,000. https://www.irs.gov/irb/2025-49_IRB (retrieved 2026-10-18)",
    "IRS, 401(k) and profit-sharing plan contribution limits ($72,000 in 2026, $80,000 with catch-up or up to $83,250 at ages 60 to 63; deferrals to all plans are added together; compensation limited to $360,000). https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-topics-401k-and-profit-sharing-plan-contribution-limits (retrieved 2026-10-18)",
    "IRS, Publication 15 (2026): Social Security wage base $184,500, rates 6.2% and 1.45% (doubled for self-employment tax on Schedule SE, 92.35% of net profit). https://www.irs.gov/publications/p15 (retrieved 2026-10-18)"
  ],
  "related": [
    "self-employment-tax",
    "401k",
    "roth-401k",
    "ira",
    "qbi-deduction"
  ],
  "changelog": []
}