How this is calculated

• Uses the actual 2026 IRS federal tax brackets and standard deduction (Revenue Procedure 2025-32), including the additional standard deduction for filers 65+ and the temporary OBBBA senior deduction (up to $6,000 per qualifying person, phasing out above $75,000 single / $150,000 joint income).
• Social Security taxability uses the standard simplified version of the IRS Social Security Benefits Worksheet: up to 50% of your benefit becomes taxable once your "combined income" (other income + tax-exempt interest + half your Social Security) crosses $25,000 single / $32,000 joint, and up to 85% becomes taxable above $34,000 single / $44,000 joint. These thresholds are fixed by law and not adjusted for inflation.
• Long-term capital gains are taxed at their own rates (0%/15%/20%), stacked on top of your ordinary taxable income — so capital gains can get pushed into a higher bracket by your other retirement income, even though they're never taxed as ordinary income themselves.
• The 401(k)/IRA/pension effective rate is calculated by comparing your total tax with and without that withdrawal — this correctly captures the withdrawal's side effect of making more of your Social Security taxable, not just its own bracket.
• This is federal tax only. It does not include state income tax, the Net Investment Income Tax, FICA/payroll tax, or any tax credits. It's a planning estimate, not a tax return — a real filing depends on details this tool doesn't ask about.