Maximum total solo 401(k) contribution from net self-employment profit
| Net self-employment profit | $120,000 |
|---|---|
| Your age | 45 |
| Own Social Security wages in 2026 | $0.00 |
| Employee deferrals used in other coordinated plans | $0.00 |
| Maximum total solo 401(k) contribution | $46,804 |
| Employer profit-sharing contribution | $22,304 |
The limits are set each year and the exact calculation follows IRS rules that depend on entity type, since S corporation owners use W-2 wages instead of net profit. The deduction reduces income tax but not self-employment tax. Balances over $250,000 require an annual filing.
This 2026 estimate is for a sole proprietor using net business profit, not an S-corporation owner’s W-2 contribution calculation. It coordinates your own Social Security wages with the $184,500 wage base when estimating the deductible half of regular self-employment tax. Enter employee deferrals already used in other coordinated plans so the individual deferral ceiling is not counted twice.
Solo 401(k) Contribution: formula
IRS: self-employed individuals tax center · IRS: inflation-adjusted tax items by year · IRS: One-participant 401(k) plans · IRS Publication 560: Small-business retirement plans · IRS Publication 15 (2026): Social Security wage base · IRS: 401(k) and profit-sharing contribution limits
Common error: Assuming a solo 401(k) caps out at the same limit as a simple IRA. The two-part employee-employer structure typically allows meaningfully more total contribution capacity than a single-role retirement account.
Solo 401(k) Contribution: changing Net self-employment profit
| Net self-employment profit | Maximum total solo 401(k) contribution | Employer profit-sharing contribution |
|---|---|---|
| $96,000 | $42,344 | $17,844 |
| $108,000 | $44,574 | $20,074 |
| $120,000 (example) | $46,804 | $22,304 |
| $132,000 | $49,035 | $24,535 |
| $144,000 | $51,265 | $26,765 |
Solo 401(k) Contribution: compare input ranges
| Input | Tested from | To | Maximum total solo 401(k) contribution: low input | Maximum total solo 401(k) contribution: high input | Swing |
|---|---|---|---|---|---|
| Your age | 41 | 50 | $46,804 | $54,804 | $8,000 (17%) |
| Net self-employment profit | $108,000 | $132,000 | $44,574 | $49,035 | $4,461 (9.5%) |
| Employee deferrals used in other coordinated plans | $0.00 | $1.00 | $46,804 | $46,803 | $1.00 |
| Own Social Security wages in 2026 | $0.00 | $1.00 | $46,804 | $46,804 | $0.00 |
Solo 401(k) Contribution: individual input comparisons
| Input | Value | Maximum total solo 401(k) contribution | Employer profit-sharing contribution |
|---|---|---|---|
| Net self-employment profit | $96,000 | $42,344 | $17,844 |
| $108,000 | $44,574 | $20,074 | |
| $120,000 | $46,804 | $22,304 | |
| $132,000 | $49,035 | $24,535 | |
| $144,000 | $51,265 | $26,765 | |
| Your age | 36 | $46,804 | $22,304 |
| 41 | $46,804 | $22,304 | |
| 45 | $46,804 | $22,304 | |
| 50 | $54,804 | $22,304 | |
| 54 | $54,804 | $22,304 | |
| Own Social Security wages in 2026 | $0.00 | $46,804 | $22,304 |
| $0.00 | $46,804 | $22,304 | |
| $0.00 | $46,804 | $22,304 | |
| $1.00 | $46,804 | $22,304 | |
| $2.00 | $46,804 | $22,304 | |
| Employee deferrals used in other coordinated plans | $0.00 | $46,804 | $22,304 |
| $0.00 | $46,804 | $22,304 | |
| $0.00 | $46,804 | $22,304 | |
| $1.00 | $46,803 | $22,304 | |
| $2.00 | $46,802 | $22,304 |
Maximum total solo 401(k) contribution: Net self-employment profit against Your age
| Net self-employment profit / Your age | 36 | 45 | 54 |
|---|---|---|---|
| $96,000 | $42,344 | $42,344 | $50,344 |
| $108,000 | $44,574 | $44,574 | $52,574 |
| $120,000 | $46,804 | $46,804 | $54,804 |
| $132,000 | $49,035 | $49,035 | $57,035 |
| $144,000 | $51,265 | $51,265 | $59,265 |
Solo 401(k) Contribution: values and definitions
| Quantity and definition | Value used |
|---|---|
| Net self-employment profit | $120,000 |
| Your age — Determines the available catch-up contribution: none under 50, $8,000 at 50-59, and the SECURE 2.0 $11,250 "super catch-up" at 60-63. | 45 |
| Own Social Security wages in 2026 | $0.00 |
| Employee deferrals used in other coordinated plans | $0.00 |
| Maximum total solo 401(k) contribution | $46,804 |
| Employer profit-sharing contribution | $22,304 |
Your age: half and double
| Your age | Maximum total solo 401(k) contribution |
|---|---|
| 22.5 | $46,804 |
| 45 | $46,804 |
| 90 | $54,804 |
A solo 401(k) lets the same self-employed person contribute in two separate capacities, as employee and as employer, and the two contributions are governed by different rules and limits. Treating the plan as a single flat contribution cap misses meaningful additional capacity the two-part structure allows.
Calculate the employee deferral and the employer profit-sharing contribution separately against their own limits, rather than estimating one combined figure.
Compare with the SEP-IRA and IRA options on the retirement calculators, and see the self-employment tax and QBI pages for the tax picture. The 401(k) contribution calculator covers employer plans, and the retirement savings page projects the balance. A plan provider can set up the account in a few days.
Understand the quantities in this calculation
Does this work for an S-corporation owner?
Not from Schedule C profit. Corporation contributions use the applicable compensation and employer rules; this tool models a sole proprietor.
Must every new solo plan be adopted by December 31?
There is a special post-year-end first-year rule for a sole proprietor with no employees. IRS Publication 560 describes adoption and elective-deferral deadlines without extensions for that case. Established-plan election rules differ.
Does age change the 2026 limit?
The model uses the ordinary age-50 catch-up of $8,000 and the higher $11,250 catch-up for ages 60–63. Eligibility and plan terms still apply.