Calculators
Each one answers a single question with a number, shows its working, and says what it does not cover.
- RSU Withholding Shortfall Calculator
What your employer withheld on an RSU vest against what the vest actually costs: federal income tax, and the 0.9% Medicare surtax your employer may never have withheld at all.
- Roth Catch-Up Mandate Calculator
From this year, higher earners must make catch-up contributions as Roth. Whether that reaches you, what the lost deduction costs, and why a plan with no Roth option stops you contributing at all.
- Super Catch-Up Calculator, Ages 60 to 63
For four years your catch-up limit is higher, and then it is not. What the window is worth this year, what it is worth across all four, and the year it shuts.
- 401(k) True-Up Calculator
Reaching the annual 401(k) limit early stops your employer match for the rest of the year. This works out what that costs, whether your plan's true-up pays it back, and which of the three ceilings actually stopped you.
What is coming
Each calculator is finished before the next one starts: the math, tests against the source documents, a written explanation, and its own statement of what it ignores. That is slower than publishing a category page and filling it in later, and it is the reason a number here can be checked.
Next up are Medicare IRMAA brackets, the 401(k) true-up trap, and the two catch-up contribution rules that changed in 2026. After those: retirement and Social Security, IRA and 401(k) limits, paycheck and withholding, student loans, and debt payoff.
Missing something you came here for? Tell us. What people looked for and did not find genuinely shapes the order.