An independent RSU planner, built to show the gap most tools miss.

Who runs this

rsuplanner.com is published by Red Goggles LLC, an independent operator of free web calculators and reference tools. We are not a broker, a financial advisor, an employer, a tax-prep firm, or affiliated with the IRS or any state tax authority. We don’t sell financial products, we don’t collect leads, and we don’t take your information — the calculator runs on your device and nothing you type is sent to us.

Why this site exists

When RSUs vest, their fair market value is added to your W-2 as ordinary income and taxed at your full marginal stack. But employers default to withholding a flat 22% federal supplemental rate on that income, while most RSU recipients sit in the 32%, 35%, or 37% bracket — plus state tax, plus the 0.9% Additional Medicare Tax above the threshold. That 10–15 point shortfall is the withholding gap, and for a significant grant it’s routinely five figures. Most people discover it as a surprise tax bill in April. This tool exists to surface it in advance, dollarized, so you can close it before then.

How it’s calculated

The estimate applies published figures in the open:

• Federal income tax — 2026 IRS brackets (Rev. Proc. 2025-32). We stack your RSU income on top of your W-2 base and other income so the tax reflects your true marginal rate, not the flat 22% supplemental rate.
• The 22% vs 37% supplemental withholding rule — under IRC §3402, employers withhold a flat 22% on supplemental wages, rising to 37% on cumulative supplemental wages above $1,000,000 in a calendar year. The tool models that cliff.
• Additional Medicare Tax (0.9%) — applied to earned income above $200,000 (single) / $250,000 (married filing jointly) / $125,000 (married filing separately), per the statutory thresholds.
• State income tax — approximated at a representative top marginal rate using published state supplemental withholding rates (for example, California’s 10.23% flat supplemental rate against a top marginal rate up to 13.3%). It excludes local and city taxes.
• Capital gains after vest — your cost basis is the FMV at vest; only the change in price after vest is a capital gain (long-term above one year, otherwise short-term).

The full method is spelled out on the calculator page under How RSUs are actually taxed.

How we stay neutral and current

We model current enacted federal law and state the mechanics factually — the 22% under-withholding isn’t a mistake or a loophole; it’s the default behavior of supplemental-wage withholding, with a clean fix (updated W-4 or an estimated payment). We don’t moralize about whether to hold or sell your shares; we surface the numbers and leave the call to you. Federal brackets, state supplemental rates, and capital-gains breakpoints update annually — we replace figures as official numbers are published, and we cite the primary sources (the IRS and your state’s department of revenue) so you can verify them yourself.

How the site is funded

rsuplanner.com is free and supported by display advertising. Advertising is kept restrained and never mixes with your inputs — see our privacy page for exactly what is and isn’t collected.

Questions or corrections? We take accuracy seriously on a topic this consequential — reach us on the contact page.