Roth Conversion Calculator

What does a Roth conversion calculator work out?

A Roth conversion calculator works out the federal income tax due when you move money from a traditional IRA or 401(k) into a Roth IRA. It adds the converted amount to your other taxable income, runs the total through the year’s ordinary-income brackets and reports the extra tax, the effective rate and the room left in your bracket.

This page also compares converting with keeping the account over a horizon you choose, and applies the Form 8606 pro-rata rule to a backdoor conversion.

How is a Roth conversion taxed, and what is bracket filling?

When you convert pre-tax funds from a Traditional IRA or 401(k) to a Roth IRA, the converted amount is treated as ordinary taxable income in the calendar year the conversion occurs. It does not qualify for preferential long-term capital gains tax rates.

Under the United States progressive tax system, your conversion dollars sit on top of your existing salary, business income, and taxable distributions. Lower federal tax brackets (10%, 12%, 22%) are filled first by your base income minus the standard deduction. The conversion amount then fills the remaining capacity of your current marginal bracket before spilling over into higher tax brackets.

A popular retirement planning strategy is bracket filling: converting only enough pre-tax assets each year to reach the ceiling of your current tax bracket (such as the top of the 22% or 24% bracket) without triggering higher marginal rates. Repeating this over several low-income years between career exit and required minimum distributions (RMDs) is known as a Roth conversion ladder.

Should I convert to a Roth IRA?

Whether converting beats keeping a Traditional IRA turns on two rates: the rate you pay on the conversion today and the rate on withdrawals later. If the two are equal and the tax is withheld from the IRA, both paths end with identical after-tax wealth — $150,918 either way on $50,000 at 7% over 20 years at 22%.

The page shows the break-even future rate at which the paths tie; nobody knows that future rate, which is why this is a comparison, not a verdict.

Paying the conversion tax from outside savings changes the arithmetic. The tax money would otherwise have sat in a taxable account losing part of its return to tax each year; moving its value into the Roth, where it compounds untaxed, is worth $7,619 on the example above with a 15% drag. The break-even future rate falls to 18.1% as a result.

Conversely, withholding the tax directly from the IRA shrinks the starting balance that compounds over time. For individuals under age 59½, funds withheld from the IRA to pay taxes are generally treated as an early distribution subject to a 10% penalty under IRC §72(t).

How do the backdoor Roth and the Form 8606 pro-rata rule work?

High earners whose modified adjusted gross income exceeds annual IRS limits cannot make direct contributions to a Roth IRA. The backdoor Roth IRA strategy involves making a nondeductible contribution to a Traditional IRA and subsequently converting those funds to a Roth IRA.

If you have zero pre-tax dollars across all Traditional, SEP, and SIMPLE IRAs, the conversion is completely tax-free. However, if you hold pre-tax IRA balances, the IRS applies the pro-rata rule under IRC §408(d)(2) and IRS Form 8606.

The IRS aggregates all of your non-Roth IRAs as of December 31 of the conversion year. You cannot choose to convert only your after-tax nondeductible basis. Instead, every conversion takes a proportionate slice of pre-tax earnings and after-tax basis. For example, if your total IRA balance is $100,000 including $7,000 of nondeductible basis, a $7,000 conversion is 93% taxable ($6,510) and only 7% tax-free ($490).

What are the two 5-year rules for Roth conversions?

Roth IRAs have two 5-year rules that run independently. The first covers earnings: to withdraw them tax-free and penalty-free, at least five tax years must have passed since 1 January of the tax year of your first Roth IRA contribution, and you must be at least 59½ (or qualify for a statutory exception).

The second rule is the 5-Year Rule for Conversions: each separate Roth conversion has its own 5-year clock starting on January 1 of the year of conversion. If you withdraw converted principal before reaching age 59½ and before that specific conversion has aged 5 full tax years, the distribution is subject to a 10% early withdrawal penalty on the taxable conversion amount under IRC §72(t).

Importantly, Roth IRA distribution ordering rules always treat original regular contributions as withdrawn first (tax-free and penalty-free at any time), followed by conversions on a first-in, first-out basis (taxable portion first), and earnings last.

Does a Roth conversion raise Medicare premiums (IRMAA)?

It can. A conversion raises your modified adjusted gross income (MAGI), and Medicare sets Part B and Part D premiums from the MAGI on your return two years earlier. For 2026 the Part B surcharge starts when 2024 MAGI was over $109,000 single or $218,000 joint: $81.20 a month on top of the $202.90 standard premium.

The surcharge rises through tiers at $137,000, $171,000, $205,000 and $500,000 (joint: double, with $750,000 at the top).

The tiers are cliffs: one dollar over a threshold sets the higher premium for both spouses for a whole year. This page marks the tier your post-conversion MAGI lands in and the surcharge it would carry, using the published 2026 tiers as the reference (the tiers are indexed each year, so the 2028 thresholds will be a little higher).

Additionally, large conversions may increase the taxable portion of Social Security benefits (up to 85% under IRS Pub 915) or trigger the 3.8% Net Investment Income Tax (NIIT) on investment gains. Multi-year conversion planning helps smooth taxable income below these critical thresholds.