Solo 401(k) contribution calculator
How much can a self-employed person put into a solo 401(k)?
On $90,000 of net profit the limit is $41,228: $24,500 as your own elective deferral plus $16,728 from the business. The business share is 20% of net earnings, not 25% — Publication 560 reduces the plan rate because the contribution itself lowers the income it is computed from.
United States · tax year 2026 · sole proprietor or single-member LLC, no employees
Your limit is not a percentage of your profit. The contribution reduces the earnings it is measured against, so the IRS reduces the rate instead — and half your self-employment tax comes off before any of it starts.
Your numbers
Profit after business expenses and before any retirement contribution. Not gross revenue.
The age you reach during the calendar year — the catch-up follows the whole year, not your birthday.
From a day job, the social security wages box of your W-2. Wages already used part of the social security wage base, which changes your self-employment tax.
Elective deferrals you already made to another employer's 401(k) this year. The annual deferral limit belongs to the person, not to the plan.
What you may contribute
Where the number comes from
Publication 560 does it in this order, and so does this page.
| Step | Amount |
|---|---|
| Net profit | — |
| Less half of self-employment tax | — |
| Net earnings from self-employment | — |
| Business contribution | — |
| Your elective deferral | — |
| Annual additions | — |
| Catch-up | — |
| Total you may contribute | — |
What age does to the answer
The catch-up is a window, not a staircase. Ages 60 to 63 get the higher amount and 64 goes back to the ordinary one — the same profit, a different year of life.
| Age | Catch-up | Total |
|---|
- Roth treatment inside the plan, and the Roth-only catch-up rule for high earners.
- Plans with employees — a solo 401(k) stops being one the day you hire.
- S corporations and partnerships, where pay is a W-2 salary and the reduced rate does not apply at all.
- Deadlines for opening and funding the plan, and Form 5500-EZ.
- State taxes.
Every limit on this page comes from IRS Notice 2025-67 and Publication 560; each one is named with its source in the calculator's own reference file.
This is a calculator, not tax advice. It shows the federal contribution limit for a one-participant plan and nothing else about your return.
Want the whole tax picture, not just the limit?
The tax engine works out what you actually owe for the year: self-employment tax, income tax, the qualified business income deduction and each quarterly payment, with every constant sourced.
US Self-Employed Tax Engine — $29Questions people actually ask
Why is the business contribution not 25% of my profit?
Because the contribution is part of the pay it is measured against. A plan that calls for 25% of compensation gives the owner 20% of net earnings, and Publication 560 gives the rate table that does the conversion. On the figures above, 25% applied straight would say $20,911; the correct answer is $16,728, a difference of $4,183.
What exactly are net earnings from self-employment?
Your net profit less the deductible half of self-employment tax. On the numbers above that is $90,000 less $6,358, which leaves $83,642. The business contribution is then a percentage of that, not of the profit you started with.
What is the annual additions limit?
It is the ceiling on everything that lands in the account for the year apart from the catch-up: your own deferral plus the business contribution. For 2026 it is $72,000. On the figures above the two together come to $41,228.
I turn 64 this year. Do I still get the higher catch-up?
No. The higher catch-up applies only to the years you are 60 through 63. At 64 it drops back to the ordinary catch-up amount. It is a window that opens and closes, which is why the table above shows both edges.
I have a job and a business. Can I defer the full amount in both?
No. The elective deferral limit belongs to you, not to each plan: what you defer at a job and what you defer in your own plan share one annual limit. The business profit-sharing contribution is separate and is not affected. Enter what you already deferred elsewhere and the deferral line above adjusts — here it is $24,500.
