Solo 401(k) and SEP IRA Contribution Calculator

How to do it

1. 1
   Step 1: Open Solo 401(k) and SEP IRA Contribution Calculator and add your input

   Type your numbers or text, add your file, or pick the options you need. Nothing is uploaded: everything stays in your browser.

2. 2
   Step 2: What Solo 401(k) and SEP IRA Contribution Calculator does

   Calculate how much a self-employed person can put into a solo 401(k) or a SEP IRA.

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   Step 3: Read the result and compare

   The result appears at once. Change one value to see how the answer moves, then keep the figure that fits your case.

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   Step 4: Copy or save it

   Copy the result or download it. For an important decision, confirm it with the official source or an adviser.

About this tool

Enter your net self-employment profit (or, for an S corporation, your W-2 wages), your age and the year. The calculator subtracts half of your self-employment tax, applies the employee deferral limit, the employer 20% (or 25%) share and the catch-up amount, and compares the total with a SEP IRA.

Sole proprietor or LLC

Your plan earnings are net profit minus half of self-employment tax. The employer share is 20% of those earnings (the 25% rate, applied after the contribution itself is deducted). You can also defer up to $24,500 in 2026 ($23,500 in 2025) as an employee, up to your earnings.

S corporation

The employer share is 25% of your W-2 wages, and you defer from your wages. The compensation counted is capped at $360,000 in 2026 ($350,000 in 2025).

Overall limits

Deferral plus employer money cannot exceed $72,000 in 2026 ($70,000 in 2025). Catch-up contributions are on top: $8,000 at 50 and over, $11,250 at ages 60 to 63 in 2026. A SEP IRA allows only the employer share, so a solo 401(k) usually lets you save more at modest incomes.

Worked example

A sole proprietor aged 45 with $100,000 of profit in 2026: half of self-employment tax is $7,065, plan earnings are $92,935, the employer share is $18,587 and you can add $24,500 of your own deferrals, for $43,087 in total. A SEP IRA would allow $18,587.

Tips for best results

Check every box before you rely on a result, because one wrong digit changes the whole answer. Use the exact figures from your payslip, bill, certificate or contract, and keep a note of the date you calculated. Rates, thresholds and rules change from time to time, so for tax, fees and legal matters treat the output as an estimate and confirm with the official source named on this page. You can run as many scenarios as you like; nothing is saved or sent, and refreshing the page clears the boxes.