Best Retirement Planning Software for Roth Conversions (2026)

An early-retiree couple did a Roth conversion and lost $86,400 in ACA premium tax credits. The tax on the conversion wasn't what hurt them. The extra income pushed them over a subsidy cliff they didn't see coming (24/7 Wall St., May 2026). So when you look for the best retirement planning software for Roth conversions, the real question is simple: will the tool show you the cliff before you go over it?

Here's the short answer. Then we'll get into what most "best of" lists leave out.

The best retirement planning software for Roth conversions: quick answer

• Most DIY planners: Boldin. Its Roth Conversion Explorer offers four optimization strategies, but you only get it on the paid PlannerPlus tier.
• Minimizing lifetime taxes: MaxiFi. Its optimizer tests many conversion sequences. Reviewers call it powerful but not very intuitive.
• Detailed federal and state tax modeling: Pralana. It's thorough, and it takes time to learn.
• Uncertainty testing: ProjectionLab. It combines historical backtesting with Monte Carlo simulation, and it's also harder to learn.
• Financial advisors: Income Lab, Holistiplan or RightCapital. These are platforms built for a practice, not for a household.
• Free starting points: Vanguard and Fidelity calculators, plus a free plan for Schwab clients. They're fine for a rough check. Don't expect optimization.

One caveat up front. Most of the pages that rank for this search are written by the vendors themselves, and the rest are generic scored lists. We couldn't find any independent head-to-head test that ran the same household through every tool. Read every comparison, including this one, with that in mind.

Price and fit at a glance

Prices change and sources disagree. Boldin's own page and a 2026 independent review give different numbers for the same tier. Check the vendor's checkout page before you pay.

What a Roth conversion tool actually has to model

Converting money to a Roth raises your modified adjusted gross income (MAGI) for that year. Higher MAGI sets off other costs that have nothing to do with your tax bracket. A tool that only calculates income tax is missing most of the picture.

IRMAA: the Medicare surcharge cliff

The standard Medicare Part B premium for 2026 is $202.90 a month. Once MAGI goes above $109,000 (single) or $218,000 (joint), IRMAA (Income-Related Monthly Adjustment Amount) applies. At the first tier, Part B rises to $284.10 and a $14.50 Part D surcharge is added. It works as a cliff, not a slope. Going $1 over the line puts you in the full tier (The Finance Buff; Q3 Advisors).

At the top tier, above $500,000 single or $750,000 joint, Part B reaches $689.90 plus a $91.00 Part D surcharge (Income Lab IRMAA guide).

The ACA subsidy cliff is back

The enhanced premium tax credits expired at the end of 2025. In 2026, MAGI above 400% of the federal poverty level wipes out the credit completely. One estimate puts that line at about $62,600 for a single filer and $124,800 for a household of four (Bridge to FI). Another puts it at about $128,600 for four, depending on which year's poverty figures are used (CoverageMath).

If you retire before 65 and buy coverage on the marketplace, this cliff matters more than any other.

The tax torpedo

Conversion income can also make more of your Social Security benefit taxable. Your effective marginal rate across that income range ends up well above your stated bracket (The Finance Buff).

Lookback timing

ACA subsidies are based on your current-year MAGI. IRMAA is based on income from two years earlier. So a conversion at 63 can raise your Medicare premiums at 65. Ask any tool you're considering whether it models that lag. We found no comparison that checks.

The widow's penalty

When one spouse dies, the survivor usually moves to single-filer tax brackets and single IRMAA thresholds, often with much of the same income. That shift is a common argument for converting while both spouses are alive. Hardly any review looks at how well tools model it, so test it yourself: run a survivor scenario and see whether the recommendation changes.

Optimizer vs. calculator

This is the most useful line to draw between tools.

• A calculator answers: "If I convert $40,000 this year, what happens?"
• An optimizer answers: "What conversion amount each year leads to the best outcome?" It also tells you what "best" means: lowest lifetime taxes, the largest estate, or the most spendable money.

Boldin, MaxiFi and Income Lab all advertise optimizers. The free tools are mostly calculators. A good calculator is often enough if you already know your target bracket ceiling and only need to check the cliffs.

Optimizers have limits too. ThinkAdvisor's "8 flaws to watch for in IRA conversion tools" (June 2025) warns that tools often assume higher income simply means a higher bracket. It also warns that fixed assumptions, such as living to exactly 95, can distort the result. An optimizer is only as good as the single future it's optimizing for.

The part most comparisons skip: uncertainty

Nearly every Roth conversion recommendation rests on assumptions you can't know yet:

• What your investments will return
• How long you'll live
• What you'll spend on health care

Change any one of them and the "optimal" conversion amount can change too. If returns are strong, your traditional IRA grows and later required distributions get larger, which makes converting look better. If returns are weak early in retirement, paying conversion tax from savings now hurts more.

Longevity matters just as much. The Social Security Administration says about one in three 65-year-olds may live to at least 90 (SSA, Retirement Information for Medicare Beneficiaries, 2026). The longer you live, the more years of tax-free Roth growth you get. Health care adds to it. Fidelity estimates $172,500 in Medicare premiums, deductibles and prescriptions over retirement for a 65-year-old retiring in 2025, and that figure doesn't include long-term care (Fidelity Investments, 2025 Retiree Health Care Cost Estimate, Jul 2025).

That's why a single average-return projection isn't enough. You want to see how a conversion plan holds up across many possible futures, not just the one where everything goes to plan.

Where Monte Climb fits

To be clear: Monte Climb is not a dedicated Roth conversion optimizer, and we won't pretend it is. If you want software that recommends a conversion amount for each year, use one of the tools above.

What we do is answer the question that comes before it: will your money last? The plan you build here runs your savings, age and monthly spending through 1,000 simulated futures (a Monte Carlo test, meaning many randomized market paths instead of one average) and gives you a success rate. The engine charges Medicare premiums and income-based surcharges year by year instead of using a flat guess. Plans run to age 95 by default, and you can extend them. Given the ThinkAdvisor warning about fixed lifespans, it's worth testing more than one end date.

Many people use the two together. A conversion tool gives you a plan. A probability engine stress-tests it: how often does your money last across 1,000 futures, and how does that compare with doing nothing? You can also ask William, our AI planner, questions like "Am I on track?" or "Is my spending sustainable?" He shows his work. It's planning software, not advice.

How to choose: a short checklist

Before you pay for anything, check that the tool:

1. Models IRMAA as tiers with cliffs, using the two-year lookback.
2. Models the 2026 ACA 400% FPL cliff, if you'll buy marketplace coverage before Medicare.
3. Captures the Social Security tax torpedo, not just ordinary brackets.
4. Handles a survivor scenario with single-filer brackets.
5. States what it's optimizing for: taxes, estate or spending.
6. Lets you vary returns and lifespan instead of locking in one path.
7. Matches your patience. MaxiFi, Pralana and ProjectionLab reward the time you put in. Boldin is easier to get started with.

Not sure where to begin? Forums like ChooseFI and HumbleDollar have honest threads from DIY retirees who've tried several of these tools.

Start with the question underneath

A Roth conversion is a bet on the future: on your tax rate, your returns and your lifespan. Before you work out how much to convert, it helps to know how solid your plan is to begin with.

It takes three numbers. Your age, your savings and your monthly spending. We'll run them through 1,000 futures and give you one clear probability. A probability, not a promise.

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Frequently asked questions

What is the best retirement planning software for Roth conversions?

For most DIY planners, Boldin's PlannerPlus tier with its Roth Conversion Explorer is the easiest optimizer to start with. MaxiFi suits people focused on lowering lifetime taxes. Pralana and ProjectionLab offer deeper modeling but are harder to learn. Advisors usually use Income Lab, Holistiplan or RightCapital.

Is there free Roth conversion software?

Yes. Vanguard and Fidelity have free calculators, and Schwab clients can get a free plan. They're useful for rough checks, but they generally calculate a conversion you choose rather than optimizing the amount year by year.

How does a Roth conversion affect Medicare IRMAA?

A conversion raises your MAGI, and IRMAA looks back two years. For 2026, surcharges start above $109,000 MAGI for single filers and $218,000 for joint filers. Going $1 over a threshold triggers the full surcharge for that tier.

Can a Roth conversion cost me ACA subsidies in 2026?

Yes. The enhanced premium tax credits expired at the end of 2025, so in 2026 MAGI above 400% of the federal poverty level removes the credit completely. That's roughly $62,600 for a single filer, according to one estimate. ACA subsidies use current-year income, so a conversion counts right away.

Does Monte Climb optimize Roth conversions?

No. Monte Climb isn't a dedicated Roth conversion optimizer. It runs your age, savings and spending through 1,000 simulated futures and gives you a probability that your money lasts. Many people use it next to a conversion tool to stress-test a plan.