Dollar Almanac

Calculators that show their work.

US tax and retirement math, worked from the IRS and Social Security documents that set each figure.

Nothing you enter leaves your browser. No account and no sign‑up.

RSU vest value

Pick one to see the gap

RSU vest value

Single filer, $220,000 salary this year, $100,000 of it from a job left in the spring.

Income tax the vest adds
$68,430.25
Withheld at the flat 22%
−$44,000.00
Medicare surtax not withheld
$900.00

Due when you file

$25,330.25

Rev. Proc. 2025-32, 2026 single brackets

Enter your own numbers

One question each, answered with a number.

Medicare IRMAA brackets are next.

Tax

Additional Medicare surtax

Your employer withholds against one threshold and you are liable on another. A couple can owe it when neither spouse would alone.

$450.00

owed by a couple at $150,000 each, with nothing withheld

RSU withholding shortfall

Payroll withholds a flat rate on a vest. Your bracket is usually higher, and the difference is due at filing.

Withheld$44,000.00
Actually owed$68,430.25

$25,330.25

owed on a $200,000 vest at $220,000 salary

Medicare

Medicare IRMAA brackets

A surcharge on Part B and Part D above an income threshold, set by your return from two years ago. It is a cliff, not a phase-in.

$1,148.40

a year, for one dollar over the first threshold

Retirement

IRA pro-rata rule

One old rollover in a traditional IRA can make a backdoor Roth almost entirely taxable, every year it sits there.

$1,562.40

tax on a $7,000 conversion beside a $93,000 pre-tax balance

Social Security wage base

Each employer caps Social Security tax separately, so two employers can withhold twice on the same band of earnings.

$2,821.00

refundable after $120,000 and $110,000 from two employers

Mega backdoor capacity

After-tax room shares one ceiling with your deferrals and your employer's money, so a better match leaves less of it.

$32,500.00

left at $250,000 pay with a $15,000 match

Roth catch‑up mandate

Higher earners must make catch‑up contributions as Roth. If the plan has no Roth option, not at all.

$1,920.00

the deduction lost, at $200,000 income

Super catch‑up, 60 to 63

Four years with a higher catch‑up limit, and it reverts the year you turn 64 whether you used it or not.

$11,250.00

instead of $8,000.00

401(k) true‑up

Reaching the annual limit early stops your employer match for the rest of the year, unless the plan trues up.

$5,000.04

match given up by front-loading at 25%

Every figure has a source.

Each number these calculators use was read from the document that sets it, by a person, on a recorded date. Where a figure has not been checked yet, the page shows nothing rather than an estimate.

  • Rev. Proc. 2025-32

    Tax brackets and the standard deduction

    Read August 19, 2026

  • IRS Publication 15 (Circular E)

    Supplemental wage withholding rates

    Read August 19, 2026

  • Notice 2025-67

    401(k) and IRA contribution limits

    Read August 19, 2026

  • SSA 2026 COLA Fact Sheet

    Social Security wage base and the COLA

    Read August 19, 2026

The rules behind the numbers.

Tax

Retirement

All guides