As an hourly financial planner, I’m always on the lookout for free tools that DIY investors can use to simplify their retirement. I recently stumbled across Vanguard’s Roth IRA Conversion Calculator (which they’ve branded as the BETR tool—Break-Even Tax Rate).

I decided to take it for a test drive to see if it’s a viable resource for someone planning to retire in 2026. Here is my honest evaluation of what works, what’s missing, and whether you should trust it with your tax strategy. You can take a look at my video on this topic here.

The "BETR" Concept: What Vanguard Gets Right

Vanguard’s tool hinges on a single acronym: BETR (Break-Even Tax Rate). The tool asks for your current income, your projected future tax rate, and how much you want to convert. It then calculates the tax rate you would need to hit in the future for a conversion today to be "worth it."

One thing I really appreciated was how it handled the "Pseudo-Roth Contribution." When you pay the taxes on a Roth conversion using cash from your bank account (rather than taking it out of the conversion itself), you are effectively making a massive, sneaky Roth contribution. You’re moving money from a taxable environment into a tax-free one. Vanguard’s tool visualizes this growth beautifully, showing how paying with outside cash makes a conversion desirable even if tax rates stay relatively flat.

The Reality Check: Where the Tool Falls Short

While the BETR tool is a great "entry-level" calculator, it quickly runs into limitations for a serious DIY retiree:

1. The Multi-Year Gap: Most of the clients I work with aren't doing a single, one-off conversion. They are looking at a 5-to-8-year "window" between retirement and Social Security or RMDs. Vanguard’s tool only allows you to model one year at a time. It doesn't help you structure a multi-year strategy.

2. Missing "Who" and "How Much": Curiously, the tool never asks how old you are, how old your spouse is, or the total size of your portfolio. Without knowing your total wealth, it can’t tell you how a $50,000 conversion affects your long-term success or your future IRMAA (Medicare) brackets.

3. The Beneficiary Factor: The tool assumes you are the one spending the money. However, for many high-net-worth families, the Roth IRA is an estate planning tool. The "break-even" isn't based on your tax rate; it’s based on your kids' tax rate 10 years after you’re gone. This tool isn't built for that level of complexity.

The Verdict: Use it for "Why," Not for "How Much"

Vanguard’s calculator is a solid "Why" tool. If you don't understand the basic math of why a Roth conversion works, 15 minutes in this calculator will make the lightbulb go off.

However, if you are trying to answer the tactical questions:

• "How much should I convert each year from age 60 to 67?"

• "How will this affect my Social Security taxation?"

• "Will this push me into a higher Medicare bracket?"

...then this tool is going to leave you hanging. For those answers, you really need a more robust system like Holistiplan, RightCapital, or a customized guardrails spreadsheet.

Need a Second Set of Eyes?

Free calculators are a great start, but they rarely capture the full "infinite loop" of retirement taxes.

At Barrett FP LLC, we offer expert financial planning on an hourly basis. We can help you move past simple calculators and build a precision tax strategy for your 2026 retirement.

[Want a professional audit of your Roth strategy? See if we’re a good fit.