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Solo 401k Calculator

Find your 2026 solo 401(k) maximum as a sole proprietor or S-corp owner, with the employee deferral, employer profit-sharing, catch-ups and the $72,000 cap, and compare it with a SEP IRA, SIMPLE IRA and 403(b).

Updated November 4, 2026. Free, no sign-up; everything runs in your browser and nothing you type is stored.

Solo 401k calculator vs SEP IRA vs SIMPLE IRA

Business typeNet profit (Schedule C) or W-2 wages ($)Age at year endDeferrals already made to another 401(k)/403(b) this year ($)

Solo 401(k) maximum for 2026

–

–Compensation used

–Employee deferral

–Employer profit-sharing

–SEP IRA maximum

–SIMPLE IRA maximum

–403(b) (if you're a nonprofit employee)

Solo 401k: two buckets of contributions

A solo 401(k) (one-participant 401(k)) lets a business owner with no employees other than a spouse contribute as both employee and employer:

Employee deferral: up to $24,500 in 2026, plus $8,000 catch-up at 50+ or $11,250 at ages 60–63. This limit is shared with any other 401(k) or 403(b) you contribute to at a day job.
Employer profit-sharing: 25% of W-2 wages for an S corporation; for a sole proprietor, effectively 20% of net profit after subtracting half of self-employment tax.
Total cap: $72,000 (Section 415(c)) plus catch-up, using compensation up to $360,000.

Example: sole proprietor, $100,000 profit, age 45: half of SE tax is $7,065, so compensation is $92,935. Employer contribution 20% = $18,587, employee deferral $24,500, total $43,087.

SEP IRA vs solo 401k

A SEP IRA allows only the employer contribution (the same 20%/25% formula, up to $72,000), so at lower incomes it allows much less than a solo 401(k): $18,587 in the example. SEP IRAs are simpler (no Form 5500-EZ when assets top $250,000), can be opened up to the tax-filing deadline, but if you have employees you must contribute the same percentage for each eligible employee earning $800 or more. People sometimes search "SEP IRAs" when comparing providers; the rules are the same everywhere.

Simple IRA

A SIMPLE IRA suits small employers with up to 100 employees: employee deferrals up to $17,000 in 2026 ($4,000 catch-up at 50+, $5,250 at 60–63; some small employers qualify for $18,100), plus a required employer match of up to 3% of pay or a 2% non-elective contribution.

403b plan for nonprofit and school employees

A 403b (403(b) plan) is the 401(k)-style plan for public schools, hospitals and 501(c)(3) nonprofits, with the same $24,500 deferral limit and catch-ups. Employees with 15+ years at the same eligible employer may get up to $3,000 a year extra (lifetime cap $15,000). If you also run a side business, your 403(b) deferrals reduce the employee deferral room in your solo 401(k).

Common questions

How much can I put in a solo 401k in 2026?

Up to $72,000 total ($24,500 employee deferral plus profit-sharing), plus $8,000 catch-up at 50+ or $11,250 at 60–63.

How is the self-employed employer contribution calculated?

20% of net profit after subtracting half of self-employment tax ($18,587 on $100,000 of profit).

Is a SEP IRA or solo 401k better?

A solo 401(k) allows more until a sole proprietor's profit reaches roughly $377,000 (where a SEP also hits $72,000), because of the employee deferral; a SEP is simpler.

What is the 2026 SIMPLE IRA limit?

$17,000, plus $4,000 catch-up at 50+ or $5,250 at ages 60–63.

Is a 403b the same as a 401k?

Similar rules and the same $24,500 limit, but for schools, hospitals and nonprofits.

Sources

General information, not financial, tax or legal advice. Check important numbers with the official source before acting on them.