Tools/Income & self-employment/Solo 401(k) Contribution Calculator✓ CHECKED AGAINST WORKED EXAMPLES · SEP 29, 2026

How much can I put into a solo 401(k) this year?

Find the most you can contribute for 2026 as both employee and employer, and the federal tax it saves.

Net profit for the year$Schedule C line 31, or your partner share, after business expenses. The starting amount is an example, not your profit.Pay from a separate job, W-2$Optional: leave at 0 to skip. It uses up the Social Security base before your self-employment tax and shares your deferral limit.Deferrals already made in another plan this year$Optional: leave at 0 to skip. The $24,500 employee limit covers all your 401(k), 403(b) and similar plans together.Your age at the end of 2026yearsPrefilled from your Money Map. From 50 you can add a catch-up contribution.

How you are paid by your business

Sole proprietor, single-member LLC or partner: the employer share is worked out from your net earnings.

Filing status

MOST YOU CAN PUT IN FOR 2026

$43,087

For 2026, as a self-employed owner with $100,000 of profit, you can put in up to $43,087: $24,500 as employee and $18,587 as employer (20% of your $92,935 of net earnings, which is your profit less half your self-employment tax). Deducted as traditional contributions, that would cut your federal income tax by about $7,814.

As employee

$24,500

As employer

$18,587

Catch-up included

Federal tax saved

$7,814

UNDERSTAND YOUR RESULT

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Terms:Self-employment tax Solo 401(k)

Where the maximum comes from

$24,500 as employee plus $18,587 as employer is $43,087, 43% of your profit. The federal tax saved, if all of it is traditional, is about $7,814, at a 22% rate on the last dollars.

Which limit sets each part

Limit	Amount	How it works
Employee deferral	$24,500	$24,500 limit
Employer: 20% of net earnings	$18,587	25% plan rate ÷ 1.25, of $92,935
Employer: 25% of the pay limit	$90,000	25% of $360,000
Employer: room under $72,000	$47,500	$72,000 in all, less the $24,500 deferral
Employer: half of what is left	$34,218	Half of net earnings after the deferral
Employer contribution allowed	$18,587	The smallest of the four

For a self-employed owner the employer part is the smallest of 20% of net earnings ($18,587), 25% of the $360,000 pay limit ($90,000), the room left under $72,000 ($47,500) and half of net earnings after the deferral ($34,218): $18,587.

The most you can put in at different profits

$25k93% of profit

$23k

$50k68% of profit

$34k

$100k43% of profit

$43k

$150k35% of profit

$52k

$250k29% of profit

$72k

$400k18% of profit

$72k

On the same age and other savings, a profit of $25,000 allows $23,234 and $400,000 allows $72,000; yours is highlighted. The $72,000 total limit, plus any catch-up, caps it for high profits.

What moves the needle

Each row re-runs the calculation with one change. Click to apply.

How it's computed

FORMULA

Net earnings N = net profit − half of self-employment tax (self-employed owner)

Employer share = the smallest of 20% × N, 25% × $360,000, $72,000 − deferral, and ½ × (N − deferral)

Employee deferral = the smaller of $24,500 − deferrals elsewhere and N − employer share; catch-up: $8,000 at 50 and older, $11,250 at 60 to 63

S corporation owner: employer share = the smaller of 25% × pay (to $360,000) and $72,000 − deferral; deferral up to pay

Tax saved = federal income tax on income − federal income tax on income less the contribution

The limits are the 2026 ones from IRS Notice 2025-67: $24,500 of employee deferrals across all your plans, $8,000 of catch-up at 50 and older ($11,250 at 60 to 63), $72,000 in all before catch-up, and $360,000 of pay counted.
A solo 401(k) is for an owner with no employees other than a spouse. If you hire someone who qualifies, the plan is no longer a one-participant plan, and other rules apply.
The federal tax saved assumes the whole amount is traditional (pre-tax) and comes off single income on the 2026 brackets after the standard deduction. The qualified business income deduction, which a contribution can shrink, and state tax are not included. Roth contributions have the same limits but save no tax now.
Self-employment tax is figured on 92.35% of profit, with the Social Security part limited by the $184,500 base after any pay from a separate job. Half of it is deducted to reach net earnings.
The deferral is assumed to be made at the maximum; the worksheet finds the employer share that goes with it. A smaller deferral raises the room for the employer share only when the half-of-earnings rule is the limit.

WORKED EXAMPLE · SAMPLE NUMBERS

Net earnings: $100,000 − $7,065 (half of $14,130 self-employment tax) = $92,935. Employer: 20% × $92,935 = $18,587, allowed $18,587. Employee: $24,500. Total $43,087.

SOURCES

[1]Publication 560, Retirement Plans for Small Business: chapter 5, Table and Worksheets for the Self-EmployedInternal Revenue Service [2]One-participant 401(k) plansInternal Revenue Service [3]Notice 2025-67: 2026 amounts relating to retirement plans and IRAsInternal Revenue Service [4]401(k) limit increases to $24,500 for 2026, IRA limit increases to $7,500Internal Revenue Service news release, November 2025 [5]Topic no. 554, Self-employment taxInternal Revenue Service [6]Rev. Proc. 2025-32: 2026 inflation-adjusted tax items (brackets, standard deduction)Internal Revenue Service, 2025

HSBuilt by Hussain Sehorewala · checked against worked examples · Sep 29, 2026

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Questions about this result

Up to $72,000 in all before catch-up: employee deferrals of at most $24,500 plus the employer share, which for a self-employed owner is at most 20% of net earnings (profit less half of self-employment tax) and for an S corporation owner 25% of pay. From age 50 you can add $8,000 of catch-up ($11,250 at 60 to 63). No one can put in more than their earnings.

Because for a self-employed owner the 25% is taken on earnings after the contribution itself is deducted. Working that back gives 20% of net earnings (25% ÷ 1.25), the “reduced rate” in IRS Publication 560. An S corporation owner is paid a salary first, so the employer share is a plain 25% of that pay.

Yes. The $24,500 employee limit is per person, across every 401(k), 403(b) and similar plan you defer into. What you defer at a job reduces what you can defer to your solo plan, but the employer share from your business is separate and still available.

A self-employed person or business owner with no employees other than a spouse, and a partner in a partnership with no other employees. If you hire employees who become eligible, they have to be included in the plan, and it is no longer a one-participant plan.

Since 2023, a sole proprietor with no employees can adopt a 401(k) after the end of the tax year, as long as it is adopted by the tax filing deadline (without extensions). To deduct a contribution for a year, it must be made by the due date of your return, including extensions.

The limits are the same. Traditional contributions come off your taxable income now, which is the saving shown on this page; Roth contributions are taxed now and grow tax-free. The employer share can also be Roth if the plan allows it.

A SEP IRA takes only the employer share, up to 25% of pay or 20% of net earnings, with no employee deferral, so at modest profits a solo 401(k) can shelter much more. At high profits both reach the same $72,000 total limit.

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