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Free Retirement Tax Tool

Roth Conversion Calculator

See exactly what a conversion costs, which brackets it fills, and how much room you have left before the next rate, the number that decides how much to convert.

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Quick Answer

A Roth conversion is taxed as ordinary income in the year you convert, no penalty, no special rate. The entire game is where the conversion lands in your brackets: convert enough to fill your current bracket, stop before the next one, repeat annually. This calculator shows the slices, the total cost, and the headroom, the same bracket-fill math behind every conversion plan we build.

Your Numbers

Example figures, replace with yours

$

Pre-tax IRA / 401(k) dollars moving to Roth this year.

$

Wages, business, pension, taxable interest, before this conversion.

Converting before a move to a no-tax state? That's a timing play.

Federal only (plus your flat state estimate), using the 2026 standard deduction and official 2026 brackets. Doesn't model Social Security taxation, IRMAA, or ACA credit effects, those matter and belong in a full projection.

Estimated Tax on This Conversion

$17,364

23.2% effective rate on the converted amount

Which Brackets It Fills

$31,800 at 22%$6,996
$43,200 at 24%$10,368
Federal Tax$17,364

The Full Picture

State tax (at your rate)$0
You end in the24% bracket
Room left in that bracket$52,875
Total Tax$17,364
Key Insight

You could convert $52,875 more at the same rate

Your conversion ends mid-bracket. If the goal is draining pre-tax dollars at today's rate, the marginal cost of converting up to the bracket ceiling is identical, leaving that room unused means doing it at a possibly higher rate later.

Watch Out

Plan how you'll pay this, before December

A conversion creates tax with zero withholding, which is how people earn underpayment penalties on an otherwise smart move. Cover it with safe-harbor quarterly estimates or a year-end withholding boost, and pay from taxable savings, not from the converted dollars themselves.

One year of this is a tactic. Ten years is a strategy.

The real wins come from a multi-year conversion plan that coordinates brackets, IRMAA, Social Security timing, and RMDs. That's a planning engagement.

Book your free 30-minute tax fit call to talk through your next steps.

Tax planning slots are limited before year-end.

Read the Backdoor Roth Guide

Worked example

A $75,000 conversion on top of $90,000 of other income, single filer

A single filer with $90,000 of wages and other ordinary income converts $75,000 of a traditional IRA to a Roth IRA in 2026 and lives in a state with no income tax. These are the calculator's own placeholder values.

Inputs

Worked example inputs
Amount to convert$75,000
Other annual income$90,000
Filing statusSingle
State tax rate0%

Calculator output

Worked example calculator output
$31,800 taxed at 22%$6,996
$43,200 taxed at 24%$10,368
Federal tax on the conversion$17,364
Effective rate on the converted amount23.2%
Bracket the conversion ends in24%
Room left in that bracket$52,875

Taxable income before the conversion is $90,000 minus the $16,100 standard deduction, or $73,900. The conversion stacks on top: the first $31,800 fills the rest of the 22% bracket and the remaining $43,200 lands in the 24% bracket. The tax is owed for 2026 with no withholding attached, so it needs an estimated payment or extra withholding.

Methodology

How this calculator works

The calculator taxes the conversion as ordinary income stacked on top of your other income, and reports the difference in federal tax with and without it.

Formulas

  • Taxable income before conversion = other income minus the 2026 standard deduction (never below zero).
  • Federal tax on conversion = tax on (taxable income + conversion) minus tax on taxable income, using the 2026 brackets.
  • State tax = conversion x your entered flat rate (capped at 15%).
  • Effective rate = (federal + state tax) / conversion amount.
  • Headroom = next bracket floor minus taxable income after the conversion.

Assumptions

  • Single or married filing jointly, taking the standard deduction.
  • All entered income is ordinary income; the whole conversion is pre-tax money (no after-tax basis on Form 8606).
  • The conversion happens in 2026 and is taxed at 2026 rates.

What it ignores

  • Capital gains and qualified dividends, which stack on top of ordinary income and can be pushed into higher rates.
  • Taxation of Social Security benefits, IRMAA Medicare surcharges, ACA premium credits, NIIT, and phaseouts that also key off income.
  • Itemized deductions, credits, the pro-rata rule for after-tax IRA basis, and state brackets.

Sources

Primary sources

  1. IRS Revenue Procedure 2025-32: 2026 tax brackets and standard deduction
  2. 26 U.S. Code Section 408A: Roth IRAs: conversion included in income, no recharacterization of conversions
  3. 26 U.S. Code Section 1: tax imposed: ordinary income tax rate schedules
  4. IRS Publication 590-A: contributions to IRAs: how conversions are reported and taxed
  5. Instructions for Form 8606: nondeductible IRAs: reporting a conversion and any after-tax basis
  6. IRS Publication 505: tax withholding and estimated tax: paying the tax a conversion creates

Written by Bryan Martin, CPA, Managing Partner and Founder of Taxstra. Last reviewed October 20, 2026. Taxstra is a CPA firm serving 1,000+ clients in all 50 states.

Educational, not individualized tax advice.

Bracket-Fill: How Smart Conversions Are Sized

Every conversion is a bet that today's rate beats tomorrow's. Since the converted dollars stack on top of your other income, the smart play is rarely "convert everything", it's convert exactly enough to fill the bracket you're comfortable paying, every year, until the pre-tax balance is where you want it. A retiree with $60,000 of income might fill the 22% bracket annually for a decade rather than face 32%+ RMD-driven rates at 75.

The multi-year version is the Roth conversion ladder: a planned sequence of annual conversions, each sized to a target bracket. Early retirees add a second motive, each year's conversion becomes penalty-free accessible after its own five-year clock, creating a rolling pipeline of spendable funds before 59½. Ladders interact with everything: estimated payments (each conversion year needs a payment plan), ACA premium credits, IRMAA at 63+, and the 0% capital gains bracket you might be filling with the same room.

Still working and high-income? The conversion math connects to two cousins worth knowing: the backdoor Roth IRA (small annual conversions that route around the income limits) and the mega backdoor Roth (after-tax 401(k) dollars converted at near-zero tax cost). If you're still deferring into a 401(k) each year, the same rate logic drives the roth vs traditional 401k decision on new contributions, not just past conversions.

Key Insight

Market dips are conversion sales

Converting 1,000 shares at $80 instead of $120 moves the same future recovery into the Roth for 33% less tax. Volatile years are when conversion plans earn their keep, but only if the plan exists before the dip shows up.

Common Questions

How much tax will I pay on a Roth conversion?

The converted amount is added to your ordinary income and taxed at your regular federal brackets (plus state income tax where applicable). There's no penalty and no special rate, a $100,000 conversion on top of $150,000 of income is taxed exactly like $100,000 of extra salary. The planning skill is sizing the conversion to fill your current bracket without spilling into the next one.

When does a Roth conversion make sense?

When the rate you'd pay now is lower than the rate you (or your heirs) would pay later. Classic windows: early-retirement gap years before Social Security and RMDs, a low-income business year, a market downturn (converting depressed shares moves more of the position per tax dollar), or before a known move to a higher-tax state. It rarely makes sense when the tax must be paid out of the converted funds themselves.

What is a Roth conversion ladder?

A multi-year sequence of conversions, typically sized to fill a target bracket each year. Early retirees use it two ways: to systematically drain a pre-tax IRA at low rates before RMDs begin, and because each conversion becomes penalty-free accessible after its own five-year clock, creating a rolling pipeline of accessible funds before age 59½.

Do I have to pay estimated taxes on a Roth conversion?

Usually yes, a conversion creates tax with no withholding attached, so a large one can trigger an underpayment penalty if you don't act. Best practice: pay via safe-harbor-sized quarterly estimates or a year-end withholding boost from wages or an IRA distribution, and avoid withholding from the conversion itself (anything withheld doesn't make it into the Roth, and before 59½ can itself be penalized).

Does a Roth conversion affect my Medicare premiums?

It can. IRMAA (the Medicare premium surcharge) is based on your MAGI from two years prior, so a conversion at 63 can raise your premiums at 65. The surcharge brackets are cliffs, one dollar over a threshold triggers the full surcharge tier for the year. If you're within a few years of Medicare, IRMAA belongs in the conversion model.

Can I undo a Roth conversion if I change my mind?

No. Recharacterization of conversions was eliminated by the 2017 tax law, once converted, it stays converted and the tax is owed. That makes sizing the conversion correctly the first time genuinely important, which is why we model conversions as part of a multi-year plan rather than a one-off December decision.

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