Solo 401(k) Calculator
For the self-employed: your maximum employee deferral, employer profit-sharing contribution, and combined total under the real 2026 IRS limits -- not a flat 25% guess.
Schedule C net profit (or equivalent), before any retirement plan deduction.
Capped at the IRS limit for your age: $24,500.
Employee deferral
$24,500.00
Limit: $24,500
Employer profit-sharing
$18,587.05
Max: $18,587
Combined total
$43,087.05
Limit: $72,000
Net earnings from SE
$92,935.23
SE tax: $14,130
What makes a solo 401(k) different
In a workplace 401(k), the employee's elective deferral and the employer's match or profit-sharing contribution come from two different parties. In a solo 401(k) for a sole proprietor or single-member LLC with no employees other than the owner (and, in many plans, a spouse), you're both parties, and both contributions come out of the same net self-employment income -- which is why the total possible contribution at a given income is usually much higher than a SEP-IRA or an IRA alone, especially for a freelancer or consultant whose net income isn't high enough for the employer piece by itself to matter much.
The catch is that the employer half isn't simply 25% of what your business made. The IRS (IRC section 401(c) and Publication 560's deduction worksheet) requires net profit to be reduced by the deduction for one-half of self-employment tax first, and the circular math of applying a 25% rate to compensation that's defined net of the contribution itself works out to an effective 20% rate on that reduced figure. Skip the self-employment-tax step and the number comes out too high.
How it's calculated
self-employment tax = net profit x 0.9235 x 0.153
net earnings from SE = net profit − (self-employment tax / 2)
The employee deferral is the same per-age IRS limit as any 401(k), capped at your net earnings:
employee deferral = min(desired deferral, IRS limit(age), net earnings from SE)
The employer profit-sharing contribution is 20% of that same reduced figure:
employer contribution = net earnings from SE x 20%
Finally, employee deferral plus employer contribution can't exceed the IRC section 415(c) combined limit for the year ($72,000 for 2026), though catch-up contributions sit on top of that limit rather than counting against it. At high enough income, this combined cap -- not the 20% employer formula -- becomes the binding constraint: at a $350,000 net profit and age 55 (a $32,500 employee deferral limit), the calculator's own defaults would put the employer contribution's 20% share at $65,055, but the combined limit trims the actual employer contribution to $47,500 so the total lands at exactly $80,000.
Worked example
The calculator's own defaults: $100,000 in net self-employment income, age 40, wanting to defer $24,500 as "employee."
| Self-employment tax | $14,129.55 |
| Net earnings from self-employment | $92,935.23 |
| Employee deferral | $24,500.00 |
| Employer profit-sharing (20%) | $18,587.05 |
| Combined total | $43,087.05 |
That combined total sits well under the $72,000 section 415(c) limit at this income, so neither piece is trimmed here -- plug the same numbers into the calculator above and it reconciles to the cent.
Frequently Asked Questions
What is the 2026 solo 401(k) contribution limit?
Two pieces, added together. The employee deferral is the same per-age limit as any 401(k): $24,500 under 50, $32,500 at 50-59, and $35,750 at 60-63 (SECURE 2.0's super catch-up). On top of that, you can add an employer profit-sharing contribution of roughly 20% of your net self-employment earnings. The combined total is capped at $72,000 for 2026 (the IRC section 415(c) annual-additions limit), plus any catch-up on top. Source: IRS Notice 2025-67 (https://www.irs.gov/pub/irs-drop/n-25-67.pdf).
Why is the employer contribution 20% of my income and not 25%?
25% is the rate that applies to a common-law employee's W-2 wages. For a sole proprietor or single-member LLC, the IRS defines your "compensation" as net earnings from self-employment, which has to be reduced by the deduction for one-half of your self-employment tax before the rate applies -- and once you also account for the fact that the plan contribution itself isn't part of that compensation base, the 25% employee-style rate becomes an effective 20% of your (already-reduced) net earnings. Skipping the self-employment-tax adjustment and applying 20% (or worse, 25%) straight to your gross net profit is the single most common solo 401(k) calculator mistake, and it overstates how much you can actually contribute.
How is a solo 401(k) different from a SEP-IRA?
A SEP-IRA only has the employer side -- roughly the same 20%-of-net-earnings contribution this calculator computes, and nothing else. A solo 401(k) adds the employee elective deferral on top, which is why it usually lets a self-employed person with modest net income save far more: at $50,000 of net self-employment income, a SEP-IRA caps out well under $10,000, while a solo 401(k) adds a full employee deferral on top of that same employer contribution. A solo 401(k) can also offer a Roth option and participant loans, which a SEP-IRA doesn't.
Can I use a solo 401(k) if I have a spouse or other employees?
A solo 401(k) generally works only for a business with no employees other than the owner and, in many plans, a spouse who's also an owner or employee of the same business -- add any other common-law employee and you typically need a different plan design. It also gets more complicated if you own more than one business (controlled-group and affiliated-service-group rules can force you to count contributions across all of them together), or if your business is an S-corp or C-corp, where compensation is your W-2 wage rather than net self-employment income and this calculator's formulas don't apply. This tool isn't exhaustive tax advice -- talk to a tax professional or plan provider about your specific situation before adopting a plan.
Figures on this page are estimates from the inputs you enter, not financial advice, and this site is not affiliated with any employer, plan administrator, bank or the IRS. Real accounts vary by plan rules, taxes and fees this tool doesn't model -- see the Terms.