Solo 401(k) calculator

Work out the most you can put in a one-participant 401(k) for 2026 as a sole proprietor or S-corp owner, and how much more that is than a SEP IRA.

By the Calcist team · Checked against known answers · Updated October 27, 2026

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Estimates for planning, not financial, tax or legal advice. Figures use US rules unless the page says otherwise.

Next: Simpler plan, lower limit: see the SEP IRA calculator. Choosing Roth or pre-tax deferrals? Try the traditional vs Roth calculator.

2026 solo 401(k) limits

Part	2026 limit
Employee deferral (pre-tax and Roth, all your 401(k)s combined)	$24,500, up to 100% of compensation
Catch-up, 50 or older	+$8,000
Catch-up, ages 60 to 63	+$11,250
Employer profit-sharing contribution	20% of net profit after half SE tax (sole proprietor) or 25% of W-2 pay (corporation)
Employee + employer total	$72,000, plus catch-up
Compensation that counts	$360,000

How it's calculated

Compensation (sole proprietor) = net profit − ½ SE tax
Employee deferral = smaller of $24,500 (minus deferrals at other jobs) or compensation
Employer = smallest of 20% × compensation, $72,000 − deferral, or (compensation − deferral) ÷ 2
Catch-up = smaller of your catch-up limit or what's left of compensation

This follows the IRS Publication 560 worksheet. The "÷ 2" step keeps the total from going over 100% of your compensation after the employer contribution. For a corporation, the employer part is 25% of W-2 pay (up to $360,000) and the total can't exceed W-2 pay.

Worked example

A 40-year-old sole proprietor with $100,000 of net profit: half SE tax is $7,064.775, leaving $92,935.23. Employee deferral: $24,500. Employer: 20% × $92,935.23 = $18,587.05. Total $43,087.05, versus $18,587.05 in a SEP IRA. At 61, the $11,250 catch-up makes it $54,337.05.

Things to know

Deferral limits are per person. If you also defer at a day job, the $24,500 is shared. The $72,000 limit is per unrelated employer, so the day job's plan doesn't use up your solo plan's employer room.
Roth catch-up rule. From 2026, catch-ups must be Roth if your FICA wages from that employer were over $150,000 in 2025. Sole proprietors have no FICA wages, so this doesn't apply to them.
Deadlines. Employee deferral elections generally must be made by year end; employer contributions can wait until your tax filing deadline.
Form 5500-EZ is required once plan assets pass $250,000 at year end.
One-participant plans can cover you and your spouse only. Hire eligible employees and the plan must cover them.

Sources

IRS Notice 2025-67 – 2026 deferral, catch-up, $72,000 and $360,000 limits
IRS: one-participant 401(k) plans – contribution rules, deferral limits by person, Form 5500-EZ
IRS Publication 560 – deduction worksheet for the self-employed
IRS Topic 554, self-employment tax – self-employment tax
SSA contribution and benefit base – 2026 wage base

How we checked this

Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:

Age 40, net profit $100,000: $24,500 + $18,587.05 = $43,087.05 ✓
Age 61, same profit: adds the $11,250 catch-up, $54,337.05 ✓
Age 52, net profit $300,000: $72,000 + $8,000 = $80,000 ✓
S-corp, W-2 $60,000, age 45: $24,500 + $15,000 = $39,500 ✓
$20,000 deferred at a day job: $4,500 + $18,587.05 = $23,087.05 ✓
Edge: net profit $25,000: deferral limited to compensation, $23,233.81 ✓

Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.

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Questions people ask

What is the solo 401(k) limit for 2026?

$72,000 in total from you as employee and as employer, plus a catch-up of $8,000 at 50 or older, or $11,250 at ages 60 to 63. The employee part alone is up to $24,500.

Is a solo 401(k) better than a SEP IRA?

At low and middle incomes, usually yes, because you can add the $24,500 employee deferral on top of the same employer contribution. At very high incomes both reach $72,000, and the solo 401(k) still allows catch-up.

How do S-corp owners calculate the employer contribution?

25% of your W-2 wages from the S-corporation, not the K-1 profit. Distributions don't count as compensation.

I have a 401(k) at my day job. Can I still have a solo 401(k)?

Yes. Your employee deferrals are shared across both plans ($24,500 total), but the employer contribution in your solo plan has its own $72,000 limit.

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