Solo 401(k) / SEP-IRA Contribution Calculator
Work out your maximum 2026 Solo 401(k) or SEP-IRA contribution from self-employment income, including the age-based catch-up tiers.
2026 combined employee-deferral + employer-contribution cap for a self-employed individual under 50. The employee elective-deferral portion alone is capped at $24,500; the employer profit-sharing portion is generally up to 25% of compensation (about 20% of net self-employment earnings after the self-employment-tax adjustment for a sole proprietor), with the combined total capped here. Age-based catch-up raises the combined cap to $80,000 for ages 50-59 and 64+, and to $83,250 for the SECURE 2.0 'super catch-up' ages 60-63 — none of those age tiers are modeled separately in this single capAmount field. Federal tax relief on a traditional (non-Roth) contribution equals the contributor's own marginal federal rate (10-37%, from statusRegime.incomeTax above), not a flat credit — reliefRate is deliberately left unset here rather than hard-coding one bracket.
Solo 401(k) and SEP-IRA Contribution Limits for 2026
Self-employed retirement plans let you shelter a meaningful chunk of your net earnings from current income tax, but the contribution limits and rules differ between a Solo 401(k) and a SEP-IRA — and both changed for 2026. This calculator works out your maximum contribution under each option from your actual self-employment income.
For 2026, the combined Solo 401(k) cap (employee deferral plus employer profit-sharing contribution) is $72,000 for someone under 50, made up of up to a $24,500 employee elective deferral plus an employer profit-sharing portion generally up to 25% of compensation. Catch-up contributions raise that combined cap to $80,000 for ages 50-59 and 64+, and to $83,250 for the SECURE 2.0 super catch-up available at ages 60-63 — this calculator does not separately model those age tiers. A SEP-IRA, by contrast, has no employee-deferral option at all: it's capped at the lesser of $72,000 or 25% of compensation, funded entirely by employer-side contributions.
Solo 401(k) vs SEP-IRA
- A Solo 401(k) lets you contribute as both employee (up to $24,500 elective deferral for 2026) and employer (profit-sharing, generally up to 25% of compensation), with a combined 2026 cap of $72,000 under age 50
- A SEP-IRA only allows the employer-side contribution — up to the lesser of $72,000 or 25% of compensation for 2026 — with no separate employee-deferral option, which usually makes the Solo 401(k) allow a larger contribution at lower income levels
- For a self-employed sole proprietor, the 25%-of-compensation figure works out closer to roughly 18.6-20% of net self-employment earnings once the required self-employment tax adjustment is applied — a nuance a simple percentage figure doesn't show on its own
- Federal tax relief on a traditional (pre-tax) contribution equals your own marginal federal rate under the 2026 brackets, from 10% up to 37% — there's no flat percentage credit
