1. Your business and age
Net profit is your Schedule C net profit (or a single-member LLC's equivalent), before this retirement contribution — not gross revenue.
2. Optional adjustments
The elective-deferral limit is shared across every 401(k) you contribute to — including a separate W-2 employer's plan — not per plan. Enter what you have already deferred elsewhere this year if any.
Enter your net profit and age, then click Calculate.
Result
What this does not cover
- Sole proprietor / single-member LLC only. This applies the net-self-employment-earnings formula for a Schedule C filer with no W-2 wages from the business. An S-corp or partnership uses a different formula (W-2 wages or a K-1 allocation) and this tool does not compute it.
- Not a Schedule SE substitute. This ignores the additional 0.9% Medicare surtax above $200,000/$250,000 and does not account for multiple businesses or controlled-group rules.
- Roth, after-tax, and mega-backdoor splits are not modelled. This computes the total contribution room, not how to split it between traditional, Roth, or (if your plan allows it) after-tax employee contributions.
- Point-in-time 2026 figures. These limits are re-indexed annually; confirm the current year's figures before relying on this in a later year.
Common questions
What is the 2026 Solo 401(k) contribution limit?
The employee elective deferral is $24,500 for 2026 ($32,500 with the age-50 catch-up, or $35,750 with the SECURE 2.0 enhanced catch-up for ages 60-63). Added to a 20% employer profit-sharing contribution from net self-employment earnings, the combined total is capped at $72,000, or $80,000 with the standard catch-up, or $83,250 with the enhanced 60-63 catch-up.
How is the employer profit-sharing contribution calculated for a sole proprietor?
Net profit minus half of self-employment tax gives net earnings from self-employment. A plan stating a 25% employer contribution rate converts to an effective 20% rate applied to that net-earnings figure for a sole proprietor or single-member LLC, because the contribution is itself computed on earnings net of the contribution.
Does the elective-deferral limit apply separately to a Solo 401(k) and a W-2 job's 401(k)?
No. The elective-deferral limit applies per person across every 401(k) plan combined, including a separate employer's plan. Deferrals already made at a W-2 job reduce the room left for the Solo 401(k) dollar for dollar.
What is the enhanced catch-up for ages 60-63?
SECURE 2.0 gives ages 60, 61, 62, and 63 an $11,250 catch-up for 2026 instead of the standard $8,000 catch-up — it replaces rather than stacks with the standard amount, and the plan document must specifically allow it.
Is this tax advice?
No. This tool applies published 2026 IRS figures to the numbers you enter, scoped to a sole proprietor or single-member LLC with no W-2 wages from the business. It does not replace IRS Publication 560 or a qualified tax professional, and an S-corp or partnership uses a different formula entirely.