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How much can I put in a solo 401(k)?

Type your 2026 net profit and your age. The solo 401k calculator works through the IRS worksheet for the self-employed and shows the most you can put in.

Your numbers

Your age at the end of 2026
More options
Most you can contribute
$43,087.05

With $100,000.00 of net profit, you can put up to $43,087.05 into a solo 401(k) for 2026.

Employer contribution
$18,587.05
Elective deferrals
$24,500.00
Catch-up contributions
$0.00
Net earnings from self-employment
$92,935.23
Self-employment tax
$14,129.55
Deduction for half of self-employment tax
$7,064.78

Most you can contribute: $43,087.05. With $100,000.00 of net profit, you can put up to $43,087.05 into a solo 401(k) for 2026.

Most you can contribute by net self-employment profit

The results are estimates for information only. They are not financial, tax, or legal advice. Check the numbers with your lender or a qualified professional before you decide. Terms of use

How to calculate

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.

Example with the default inputs (Net self-employment profit $100,000.00, Your age at the end of 2026 Under 50, Employer contribution rate 25%): With $100,000.00 of net profit, you can put up to $43,087.05 into a solo 401(k) for 2026.

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.

  • 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.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Net self-employment profit $100,000.00, Your age at the end of 2026 Under 50, Employer contribution rate 25% gives Self-employment tax $14,129.55, Deduction for half of self-employment tax $7,064.78, Net earnings from self-employment $92,935.23, Employer contribution $18,587.05, Elective deferrals $24,500.00, Catch-up contributions $0.00, Most you can contribute $43,087.05.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
  2. Net self-employment profit $100,000.00, Your age at the end of 2026 60 to 63, Employer contribution rate 25% gives Employer contribution $18,587.05, Elective deferrals $24,500.00, Catch-up contributions $11,250.00, Most you can contribute $54,337.05.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
  3. Net self-employment profit $400,000.00, Your age at the end of 2026 50 to 59, or 64+, Employer contribution rate 25% gives Employer contribution $47,500.00, Elective deferrals $24,500.00, Catch-up contributions $8,000.00, Most you can contribute $80,000.00.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
  4. Net self-employment profit $30,000.00, Your age at the end of 2026 Under 50, Employer contribution rate 25% gives Net earnings from self-employment $27,880.57, Elective deferrals $24,500.00, Employer contribution $1,690.28, Most you can contribute $26,190.28.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)
  5. Net self-employment profit $100,000.00, Your age at the end of 2026 Under 50, Employer contribution rate 25%, Deferrals to other 401(k) plans (optional) $10,000.00, Social Security wages from a job (optional) $180,000.00 gives Self-employment tax $3,236.15, Deduction for half of self-employment tax $1,618.08, Elective deferrals $14,500.00, Employer contribution $19,676.39, Most you can contribute $34,176.39.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)

How it works

Self-employment tax (Schedule SE). Net earnings for the tax = 92.35% × net profit. Under $400, there is no self-employment tax. Otherwise tax = 12.4% × the smaller of those earnings and ($184,500 − Social Security wages from a job, not below $0) + 2.9% × those earnings.

Publication 560 worksheet, with the 2026 limits:

  1. Step 1: net profit.
  2. Step 2: deduction for half of self-employment tax.
  3. Step 3, net earnings = step 1 − step 2.
  4. Steps 4 and 5: net earnings × the reduced rate, rate ÷ (1 + rate) (0.20 for 25%).
  5. Step 6: $360,000 × the plan rate. Step 7: the smaller of steps 5 and 6.
  6. Step 9, deferrals: the smaller of ($24,500 − deferrals to other plans, not below $0) and net earnings. The calculator defers the most allowed.
  7. Step 10: $72,000 − step 9. Step 12: (net earnings − step 9) ÷ 2.
  8. Step 13, employer contribution = the smallest of steps 7, 10 and 12.
  9. Step 14: net earnings − step 13. Step 15: the smaller of step 9 and step 14 (the deferrals allowed).
  10. Steps 16 to 18, catch-up = the smaller of (step 14 − step 15) and the catch-up limit: $0 under 50, $8,000 at 50 to 59 or 64 and older, $11,250 at 60 to 63, less any deferrals to other plans above $24,500.
  11. Step 19, most you can contribute = employer contribution + deferrals + catch-up.

Exact arithmetic. Every amount is read as the exact decimal you typed, each step is an exact fraction, and the results are rounded once to cents, half up.

Figures that change each year

The data check should compare these with the IRS cost-of-living notice for the next year and the next Publication 15.

Figure2026 valueSourceNext update
Elective deferral limit, section 402(g)$24,500Notice 2025-67IRS cost-of-living notice for 2027 (October to November 2026)
Catch-up at 50 or older, section 414(v)$8,000Notice 2025-67Same
Catch-up at ages 60 to 63$11,250Notice 2025-67Same
Annual additions limit, section 415(c)$72,000Notice 2025-67Same
Compensation limit, section 401(a)(17)$360,000Notice 2025-67Same
Social Security wage base (self-employment tax)$184,500Publication 15 (2026)The Social Security Administration in October; Publication 15 for 2027

When the data is out of date

After December 31, 2026 the page keeps using the 2026 limits and says so above the result.

Assumptions

  • Tax year 2026; a sole proprietor or partner whose plan covers only them (and perhaps a spouse). Net profit is at most $1 billion.
  • Deferrals go to the full limit first; catch-up contributions to other plans are not included.
  • An estimate, not tax advice.

Worked examples by hand

$100,000 of profit, under 50. Earnings for the tax = 92,350; self-employment tax = 12.4% × 92,350 + 2.9% × 92,350 = 11,451.40 + 2,678.15 = $14,129.55; half = $7,064.78. Net earnings = $92,935.23. Step 5 = 20% × 92,935.225 = $18,587.05; step 6 = $90,000; step 10 = 72,000 − 24,500 = $47,500; step 12 = (92,935.225 − 24,500) ÷ 2 = $34,217.61. Employer contribution = $18,587.05; deferrals $24,500; total $43,087.05.

The same at age 61. Step 14 = 92,935.225 − 18,587.045 = 74,348.18; catch-up = the smaller of 74,348.18 − 24,500 and $11,250 = $11,250; total $54,337.05.

$400,000 of profit, age 55. Self-employment tax = 12.4% × 184,500 + 2.9% × 369,400 = 22,878 + 10,712.60 = $33,590.60; net earnings = $383,204.70. Step 7 = the smaller of 76,640.94 and 90,000; step 10 = $47,500 is smaller, so the employer part is $47,500. Deferrals $24,500 + catch-up $8,000: total $80,000.

$30,000 of profit. Self-employment tax = 15.3% × 27,705 = $4,238.87; net earnings = $27,880.57. Step 12 = (27,880.5675 − 24,500) ÷ 2 = $1,690.28, smaller than step 5 ($5,576.11), so that is the employer part. Total = 1,690.28375 + 24,500 = $26,190.28.

With a job. $10,000 deferred at work and $180,000 of Social Security wages: room under the wage base = $4,500, so self-employment tax = 12.4% × 4,500 + 2.9% × 92,350 = 558 + 2,678.15 = $3,236.15. Net earnings = $98,381.93; deferrals = 24,500 − 10,000 = $14,500; employer part = 20% × 98,381.925 = $19,676.39; total $34,176.39.

Other questions people ask

How much can I contribute to a solo 401(k) in 2026?

Elective deferrals of up to $24,500, plus an employer contribution, with the two together capped at $72,000. On top of that, a catch-up of $8,000 at age 50 or older, or $11,250 at ages 60 to 63, for totals of up to $80,000 or $83,250. Your net earnings set the real limit.

How is the employer contribution figured for the self-employed?

Start from net profit and take off half of your self-employment tax to get net earnings. The employer part is net earnings × rate ÷ (1 + rate): 20% of net earnings for a 25% plan. With $100,000 of profit, net earnings are $92,935.23 and the employer part is $18,587.05.

Why 20% and not 25%?

For the self-employed, the contribution itself comes out of the earned income it is based on. 25% of what is left after the contribution is the same as 20% of the amount before it: 0.25 ÷ 1.25 = 0.20. IRS Publication 560 calls this the reduced rate.

I also have a 401(k) at my job. Does that change anything?

Yes. The $24,500 deferral limit is per person across all your plans, so deferrals at your job use part of it; type them in the calculator. The employer contribution to your own plan has its own limit. W-2 wages also use up part of the Social Security wage base, which lowers your self-employment tax.

Can I make Roth contributions to a solo 401(k)?

If your plan allows it, deferrals and catch-up can be designated Roth contributions. They count toward the same limits, but they are not deductible.

What if my profit is small?

Contributions cannot be more than your net earnings. With $30,000 of profit, net earnings are $27,880.57: deferrals of $24,500 use most of it and the employer part is limited to half of what is left, $1,690.28, for a total of $26,190.28.

Does this work for an S corporation owner?

No. If you are paid wages by your own S corporation, the employer part is figured on your W-2 wages (up to 25%), not on net earnings from self-employment. This calculator is for sole proprietors and partners.