How to Use Solo 401(k) and SEP IRA Contribution Calculator Online for Free: Step-by-Step Guide
Calculate how much a self-employed person can put into a solo 401(k) or a SEP IRA. Free, private and no sign-up.
How to Use Solo 401(k) and SEP IRA Contribution Calculator Online for Free
Calculate how much a self-employed person can put into a solo 401(k) or a SEP IRA. This guide shows what Solo 401(k) and SEP IRA Contribution Calculator does, how to use it step by step, what to watch out for, and which related tools on shobfree.com can help next.
Quick answer
Open Solo 401(k) and SEP IRA Contribution Calculator, type your numbers or pick the options you need, check the result that appears, and then use it. Solo 401(k) and SEP IRA Contribution Calculator is free, needs no account and runs in your browser, so what you type or add stays on your device.
What Solo 401(k) and SEP IRA Contribution Calculator does
- Calculate how much a self-employed person can put into a solo 401(k) or a SEP IRA.
- Enter your net self-employment profit (or, for an S corporation, your W-2 wages), your age and the year.
- The calculator subtracts half of your self-employment tax, applies the employee deferral limit, the employer 20% (or 25%) share and the catch-up amount, and compares the total with a SEP IRA.
Enter your net self-employment profit (or, for an S corporation, your W-2 wages), your age and the year. The calculator subtracts half of your self-employment tax, applies the employee deferral limit, the employer 20% (or 25%) share and the catch-up amount, and compares the total with a SEP IRA.
How to use Solo 401(k) and SEP IRA Contribution Calculator, step by step
- Fill in the boxes. Type your numbers or pick the options you need.
- See the result. The answer updates right away as you change a value.
- Use it. Copy the result or note it down. Nothing is sent anywhere.
These three steps are the same on a phone and on a computer. If something looks wrong, change one setting and look at the result again; Solo 401(k) and SEP IRA Contribution Calculator updates as you go.
A worked example
A sole proprietor aged 45 with $100,000 of profit in 2026: half of self-employment tax is $7,065, plan earnings are $92,935, the employer share is $18,587 and you can add $24,500 of your own deferrals, for $43,087 in total. A SEP IRA would allow $18,587.
Tips for a good result
- Treat the result as an estimate and confirm important figures with the official source.
- Run a best case and a worst case, then keep both numbers for your planning.
- Change one value at a time, so you can see which input moves the result.
- Double-check the units and the currency or period before you trust a number.
Who is this for?
Solo 401(k) and SEP IRA Contribution Calculator is useful for anyone who needs calculate how much a self-employed person can put into a solo 401(k) or a SEP IRA without installing software or paying for a subscription. Students, freelancers, office staff and small-business owners use tools like this for quick, one-off jobs where a full application would be too much.
Frequently asked questions
Which profit do I enter?
Net profit from Schedule C (or your share of partnership income), before the deduction for half of self-employment tax.
Why is the employer share 20% and not 25%?
For the self-employed the 25% rate applies after the plan contribution is deducted, which works out to 20% of net earnings.
Can I contribute to a solo 401(k) and my day job's 401(k)?
Yes, but the employee deferral limit is shared between all plans.
What about a Roth solo 401(k)?
Many plans allow Roth deferrals. The limit is the same, but you pay the tax now.
Do I need to create an account to use Solo 401(k) and SEP IRA Contribution Calculator?
No. Open the page and start. There is no sign-up, no email and no payment.
Can I use Solo 401(k) and SEP IRA Contribution Calculator on my phone?
Yes. The page adapts to small screens, and everything runs in your phone's browser, so the same steps work on a laptop or a phone.
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Privacy
Solo 401(k) and SEP IRA Contribution Calculator works inside your browser. Your files, text and numbers are not uploaded to a server, and there is nothing to delete afterwards.
