An independent Roth conversion calculator, built to see the cliffs.

Who runs this

rothcliff.com is published by Red Goggles LLC, an independent operator of free web calculators and reference tools. We are not a financial advisor, broker, custodian, insurer, or government agency, and we are not affiliated with the IRS, CMS, the Social Security Administration, or any financial institution. We don't sell products, we don't collect leads, and we don't take your information — the calculator runs on your device and nothing you type is sent to us.

Why this tool exists

Most Roth conversion calculators output a single number — the federal tax on the conversion — and stop there. But a conversion isn't just a federal-tax event. It pushes your reportable income up, and income above certain thresholds trips cliffs that cost real money: a Medicare IRMAA tier can add hundreds to thousands of dollars per person to your premiums two years later; the Net Investment Income Tax can pull an extra 3.8% onto your other investment income; and — for 2026 marketplace coverage — the ACA premium-tax-credit cliff is back in force. Several of these cliffs are non-obvious, and the IRMAA two-year lookback in particular is the most-misunderstood Medicare rule online. Making those cliffs the centerpiece — not an afterthought — is the entire reason this tool exists.

How it's calculated

The estimate is assembled from published figures, applied in the open:

• Federal brackets and the standard deduction — sourced from the IRS for tax year 2025 (Rev. Proc. 2024-40, as amended) and tax year 2026 (Rev. Proc. 2025-32). The conversion is treated as ordinary income stacked on top of your other income.
• IRMAA tiers and surcharges — the Medicare Part B and Part D income-related monthly adjustment amounts, from the annual CMS announcement. IRMAA uses a two-year MAGI lookback, so a conversion this year affects premiums two years later; the tool shows that timeline explicitly.
• NIIT threshold — the 3.8% Net Investment Income Tax applies once MAGI exceeds $200,000 (Single), $250,000 (MFJ), or $125,000 (MFS). The conversion itself is ordinary income, but it can push your other investment income across the line.
• ACA premium-tax-credit cliff — modeled at the currently-applicable threshold for marketplace enrollees. Because the enhanced-subsidy rules are legislatively volatile, the tool flags the applicable rule for your planning year and points you to primary sources to confirm.
• State tax — a top-marginal estimate by state, noting that twelve states don't tax retirement distributions at all. State treatment of Roth conversions varies; verify yours with a local CPA.

The full method is laid out on the calculator page under How this works, and each cliff is explained further in our guides.

How we stay neutral and current

We don't pitch Roth conversions. A conversion is a tool, not a goal — for people in their highest-earning years it's often the wrong move, and the calculator is built to help you decide, not to sell you on converting. We model current enacted law, state the legislative history factually (for example, the ACA enhanced credits and their expiration), and avoid fear-mongering about the SECURE Act's 10-year rule. Every page carries a dated "last updated" note, and we link to primary sources — the IRS, CMS/Medicare.gov, and non-partisan trackers — so you can verify the numbers yourself. IRMAA tiers and federal brackets inflation-adjust annually; we replace estimates with official figures as they're published each fall.

How the site is funded

rothcliff.com is free and supported by display advertising. Advertising is kept calm and never mixes with your inputs — see our privacy page for exactly what is and isn't collected.

Questions or corrections? We take accuracy seriously on a topic this consequential — reach us on the contact page.