Category
Conversion headroom, withdrawal sequencing, and account-level tradeoffs.
Roth
Backdoor Roth Pro-Rata Calculator (Form 8606)
Estimate taxable vs nontaxable Roth conversion amounts using the pro-rata rule, and see how year-end IRA balances change the outcome.
On This Page
3 planning notes, 3 FAQs, and source links for follow-up.
Workflow
Start with sample inputs, review the live output, then save the assumptions you plan to act on.
Why This Tool Exists
Backdoor Roth works cleanly when your IRA balances are clean. When they are not, the pro-rata rule decides what is taxable.
This tool is built to make the rule legible: plug in your year-end IRA balance, your nondeductible basis, and your conversion amount. Then you get a directional taxable estimate and a checklist to keep your paperwork clean.
Execution note: Run the tool, then write down your assumptions and keep the receipts and logs as you go. The strategy that wins on paper only matters if your process holds up in the real world.
Pro-Rata Calculator (Planning)
Estimate taxable vs nontaxable conversion amounts using year-end IRA balances and basis.
Nontaxable portion (est.)
$0
Taxable portion (est.)
$0
Remaining basis (est.)
$0
| Line item | Amount | Execution note |
|---|
If you want clean backdoor Roth execution, plan around 12/31 IRA balances. That is the lever most people ignore until it is too late.
How Pro-Rata Works (Execution-First)
The IRS looks at all Traditional, SEP, and SIMPLE IRA balances as one combined bucket for this calculation.
Your basis is spread across the whole bucket. That means the conversion is partly taxable and partly nontaxable based on the ratio of basis to total IRA value.
The year-end balance matters. You cannot fix a pro-rata surprise after the year ends without changing facts.
Common Mistakes
Forgetting a SEP or SIMPLE IRA balance that triggers pro-rata taxation.
Not tracking basis cleanly from year to year (Form 8606 matters).
Assuming the conversion is tax-free because the contribution was nondeductible.
Execution Notes
If you want clean backdoor Roth execution, discuss your IRA balance strategy with your advisor before December.
Save your inputs, year-end statements, and Form 8606 history in one folder.
Treat this as a planning estimate. Final numbers depend on your actual 12/31 balances and your filed forms.
Documentation Checklist (Keep It Defensible)
- Create a one-page objective memo before you execute (what outcome you are trying to buy).
- Store your assumptions and calculations in a dated PDF (no year-end reconstructions).
- Keep evidence in the same folder structure every month (receipts, logs, approvals).
- Ask your CPA what would make this easy to sign off on, then build that packet.
Primary Sources To Verify Before You Act
Use primary guidance and your own records before you treat any page like a final answer. These are the source layers that should drive the decision.
- IRS retirement plan guidance and IRA rules
- Medicare premium and IRMAA guidance
- Current IRS forms, instructions, and publications for the relevant tax year
- Your actual account statements, payroll reports, entity records, and advisor memos
Frequently Asked Questions
Yes. The pro-rata rule looks at Traditional, SEP, and SIMPLE IRA balances together for this calculation.
Because the denominator of the pro-rata ratio is based on year-end IRA value plus conversions and distributions. That is why December planning matters.
It follows the core structure, but it is still a planning model. Your CPA will finalize based on your actual balances and filed forms.
Use The Tool, Then Build The Full Plan Live
Before You File runs live on Zoom from Friday, April 17, 2026 through Sunday, April 19, 2026, from 10 AM to 4 PM Eastern each day. Preston walks through how to read your 2025 return, choose the right tax and wealth moves, and leave with a dated 12-month 2026 plan.
Get Your Seat Before You FileEducational content only. Results vary based on your facts. Always consult a qualified tax professional before making decisions.