Free calculator

Roth conversion calculator

Shows how much you’d have to spend in the end if you convert — and if you don’t — side by side, after all taxes are paid. Runs entirely in your browser — no account, and your numbers never leave this page.

$8,410 moreDon’t convert comes out ahead in this example — more money left after all taxes are paid.

Convert $50,000$866,670

Don't converthigher$875,081

Roth (tax-free)IRA/401(k), after its withdrawal taxThe tax money, still yours if you don’t convert

Conversion tax owed now: $11,964

1Your money

Pre-tax balance$

Convert this year$

2Tax rates

Filing status

Your income this year$

→ the conversion is taxed at about 23.9% federal

→ reaching the 24% bracket

Yearly income in retirement$

→ withdrawals taxed at about 11% average federal

→ topping out in the 22% bracket

State income tax (optional, flat %)

Conversion%

Withdrawals%

3Time & tax money

Years until withdrawals

Assumed growth%/yr

Pay the tax from

If kept, that money would earn%/yr

Prefilled with an example — drag the sliders or type your own numbers.

Good to know

What this leaves out

Required minimum distributions (RMDs) — and if your balance is large next to the retirement income you entered, real withdrawals would climb into higher brackets than its average
How Social Security gets taxed as income rises
Medicare IRMAA surcharges, ACA subsidy cliffs, and the tax credits and 3.8% investment surtax that key off your income
State tax details a single flat rate can’t capture — some states have their own brackets, nine have no income tax, and a few (Illinois, Pennsylvania, Mississippi) generally don’t tax retirement distributions, conversions included
Multi-year conversion ladders
A surviving spouse soon files as single, with the standard deduction and most bracket thresholds at half the married amounts
What heirs would pay: most non-spouse heirs must empty an inherited account within 10 years — pre-tax money is taxed at their rates then; Roth money isn’t
The 10% penalty if conversion tax is withheld before age 59½
The 5-year rules: converted money has its own 5-year clock before penalty-free access if you’re under 59½ — and earnings have another
The after-tax yield you enter for outside money is one flat number — real accounts vary year to year, and if that money is invested with gains mostly taxed when sold rather than yearly, keeping it does a bit better than a flat rate implies

This page is a quick, directional read under the stated assumptions — arithmetic on your inputs, not advice, and not a plan. The list above is what a real decision would also weigh — the companion post walks through these trade-offs in prose: The Roth conversion math, without the hand-waving

Plain answers

Exactly how the math works

Both paths grow for the same number of years at the growth rate you chose. Pre-tax money is taxed on the way out, at the rate computed from your retirement income; Roth money isn’t taxed again. When the tax is paid from outside money, those dollars aren’t dropped from the picture — the don’t-convert side keeps them, growing at the after-tax yield you state — so nothing in the comparison rests on a hidden assumption. One fact worth knowing: if your conversion’s tax rate and your withdrawals’ tax rate were equal, and the tax came out of the converted amount, the two paths would tie exactly — taxing money before it grows or after it grows multiplies to the same number.

Why is the tax rate on withdrawals so much lower than my bracket?

Because withdrawals are taxed from the bottom up: the first chunk is tax-free (standard deduction), the next chunks at 10% and 12%, and only the last bit at your bracket. The page does this arithmetic from your retirement income — someone "in the 22% bracket" with $100,000 a year pays about 13% on average (single filer, 2026). Conversions are the opposite: they stack on TOP of your income, so converted dollars are taxed at your highest bracket(s). That asymmetry is most of why this decision is interesting.

Why can the two paths come out identical?

Multiplication doesn’t care about order. Take $10,000 at a 25% rate that never changes: pay the tax now and $7,500 grows 10x to $75,000, tax-free. Or let the full $10,000 grow 10x to $100,000 and pay 25% on the way out — $75,000 again, to the dollar. What separates the paths in real life is a rate that changes, or paying the tax from money outside the account.

Why does paying the tax from outside money change the answer?

Because the full conversion gets to grow tax-free instead of a smaller piece of it. The trade: the money that paid the tax is gone, along with whatever it would have earned if you’d kept it — the rate you set on the page. The slower that money was growing, the cheaper the trade. Paid from checking cash earning nothing, converting gets its biggest boost.

Why only two choices for where the tax comes from?

Because every real source ends up being one of these two. Paying from other pre-tax money works out essentially the same as converting a bigger amount with the tax withheld. Paying from an existing Roth trades tax-free dollars for tax-free dollars — also identical to withholding. Everything else is money outside the account, and the only thing about it that changes the answer is what it would have earned if kept — the rate you set.

Is this advice?

No. It’s arithmetic on the numbers you typed, under the assumptions listed above — it describes two possible futures side by side and leaves the judgment where it belongs, with you (or a fiduciary advisor who knows your whole picture).

The math here is meant to be checked. Spot something off, or a case you wish it handled? support@presobudget.com