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Real Marginal Rate Calculator

What does the next dollar of IRA withdrawal really cost, once Social Security and Medicare react? Every piece below can be linked to, so it opens in a window on your reader's screen, current as of the record. No form to fill in.

2026 law · Reviewed September 5, 2026 · The full page, with methodology and sources · the terms · All tools

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Social Security, other income, filing status, and a step in; the real rate on that step, what drove it, and the whole curve across the income range out. In a frame it carries no cookies, no tracking, and a visible link back to the methodology. Your site has to allow frames; most do. The link that opens it in a small window is on the professionals page.

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In plain words.
Your tax bracket says what rate the last dollar of income is taxed at. But in retirement one more dollar of income can also make more of your Social Security taxable, shrink a deduction, or push you into a higher Medicare premium tier. So the real cost of the next withdrawal is often much higher than the bracket. This tool computes that real rate on a withdrawal of any size, says what drove it, and draws the whole curve so you can see where it peaks.
Why it matters.
Withdrawals and Roth conversions are sized against the real rate, not the printed one. Seeing the curve shows where a little more income costs a lot more tax, and where it stops.
An example.
A single retiree with $30,000 of Social Security and $40,000 of other income is in the 22 percent bracket. The next $10,000 of IRA withdrawal costs about $1,680 in tax, 16.8 percent, because part of it fills a lower bracket; a little higher up the curve the rate passes 40 percent as the benefit is pulled into income.
Where it stops.
It assumes ordinary income and the standard deduction. Capital gains and dividends sit in the same stack and shift the curve, and state tax adds to every point on it.

Everything here reads from one reviewed record, so a copied piece carries its year and its review date. When the law moves, the embed updates by itself; a copied table or chart keeps the year in its caption. Corrections are welcome through the contact page.