Last updated 2026-05-02
Understand why after-tax basis can reduce but not always eliminate Roth conversion taxes.
When a traditional IRA includes both pre-tax and after-tax money, the taxable portion of a conversion is commonly affected by the pro-rata rule.
A basis ratio can estimate what share of a conversion is treated as after-tax money, but accurate reporting depends on complete IRA records and Form 8606.
Do not assume you can convert only the after-tax portion of an IRA without considering all relevant traditional, SEP, and SIMPLE IRA balances.
Use the Roth Conversion Calculator to model the concepts in this guide with your own educational assumptions.
Open the calculatorEducational overview of backdoor Roth concepts and pro-rata basis considerations.
A plain-English guide to Roth conversion basics, taxable income, and key IRS rules.
Understand the inputs that affect Roth conversion outcomes without treating a calculator as advice.
This Roth Conversion Calculator is for educational and illustrative purposes only. It does NOT constitute tax, financial, legal, or investment advice. The calculation results are based on the information you provide and the latest IRS tax rules, which are subject to change. We do not guarantee the accuracy of the results. Please consult a licensed Certified Public Accountant (CPA), financial advisor, or tax professional before making any financial decisions.