IRMAA surcharge
A conversion two years ago can raise your Part B & D premiums today. Harbor shows the surcharge tier every year and stops before it trips.
Chart a conversion across your whole retirement — taxes, Medicare surcharges, Social Security, your spending, and what's left for your family — and get one clear answer: convert, hold, or it's a close call.
A conversion doesn't just fill a tax bracket. It ripples through five other systems — Harbor charts every one of them, and marks where each turns into a hazard.
A conversion two years ago can raise your Part B & D premiums today. Harbor shows the surcharge tier every year and stops before it trips.
Cross 400% of the poverty line and you can lose your entire premium tax credit. Harbor flags the exact income ceiling.
Extra income can drag more of your Social Security into taxable territory. Harbor measures how much, at every conversion size.
Pre-tax and after-tax money together? Form 8606 basis tracking gets the taxable share right — most calculators don't.
Harbor projects every account 30 years out and compares after-tax legacy — the number that actually decides this.
The plan draws your accounts in order to fund real living costs — so the answer reflects the life you're living, not just the tax.
Income, accounts, Social Security, spending. Only what matters — sections you don't need stay hidden.
Lowest lifetime tax, most to heirs, or a blend — and any limits you care about.
One verdict, both outcomes measured the same way, and how robust it is to your assumptions.
The year-by-year schedule, with the exact limit that sizes each year — then print it.
The same five questions the tool is built to answer — spelled out here for search engines and for you.
A Roth conversion raises your MAGI, which sets your Medicare Part B and D premiums two years later. Harbor finds the largest conversion each year that stays under the next IRMAA tier, and shows the surcharge if you cross it.
Conversion income can push you over 400% of the federal poverty line, where the premium tax credit can drop off entirely. Harbor flags the exact income ceiling before the cliff.
Yes — extra income raises provisional income and can drag more of your Social Security benefit into taxation (the "tax torpedo"). Harbor measures how much of your benefit becomes taxable at each conversion size.
If your IRA holds both pre-tax and after-tax (basis) money, each conversion is taxed proportionally under the Form 8606 pro-rata rule. Harbor tracks basis so the taxable share is computed correctly.
Harbor projects every account 30 years out and compares after-tax legacy on the convert vs. hold path, netting the conversion tax and the heir's tax on inherited pre-tax dollars.
Five questions the engine is built to answer in detail, one per topic.
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The Roth logic behind this tool is guarded by over 2,000 automated tests — the same depth of modeling some paid planning tools charge for. It's free here, and your numbers never leave your device.
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