Own equity at a US company? Calculate your RSU, ESPP or Stock Option value
In the United States, “Share Incentive Plan” is generally used as a plain-language term for any employer program that grants equity — Restricted Stock Units (RSUs), Employee Stock Purchase Plans (ESPPs), or Stock Options. That’s different from the calculator above, which is built specifically for the UK’s HMRC-approved Share Incentive Plan scheme. Use the calculator on this page instead if your employer is a US company (or pays you in USD) and granted you RSUs, ESPP shares, or stock options.
Enter your grant details below to estimate the pre-tax value, an estimated tax and payroll (FICA) deduction, and the resulting net value — broken down so you can see exactly how each figure was reached.
RSUs, ESPPs and Stock Options — what’s actually being calculated
Restricted Stock Units (RSUs): shares your employer grants you outright on a vesting schedule. Once a batch vests, its full market value is generally treated as ordinary income and is subject to federal income tax and FICA (Social Security and Medicare) in the year it vests — there’s no purchase price to subtract.
Employee Stock Purchase Plans (ESPPs): let you buy company shares — often at a discount — through payroll deductions. The value you receive from the discount is typically treated similarly to ordinary income for payroll tax purposes; any further gain after purchase is usually a capital gain when you sell, which this tool does not attempt to model.
Stock Options (ISOs/NSOs): give you the right to buy shares at a fixed “strike” price. Your gain is the difference between the share price when you exercise (or the projected price this tool estimates) and your strike price — so a strike price at or above the projected share price means no gain. Options carry their own, more complex tax treatment (particularly ISOs), which this simplified tool does not fully replicate.
What this calculator assumes
- Your shares/options grow at a single, constant annual rate you choose — real markets don’t move in a straight line, so treat this as a planning estimate, not a forecast.
- Your tax rate is a flat, combined estimate (federal + state) that you enter — it does not calculate marginal tax brackets, standard deductions, or state-specific rules.
- FICA (7.65% by default: 6.2% Social Security + 1.45% Medicare) is applied to RSU and ESPP value up to the Social Security wage base, and is not applied to stock option gains, which are typically not subject to FICA.
- It does not account for AMT (relevant to ISOs), the Additional Medicare Tax on high earners, employer withholding elections, or your specific plan’s vesting cliff/schedule beyond a simple total number of years.
These figures are configurable by the site owner in Dashboard → SIP Calculator and are checked periodically — see the “last checked” date in the footer.
A worked example: 500 RSUs over 4 years
Say your employer grants you 500 RSUs when the share price is $40, vesting evenly over 4 years, and you expect the stock to grow around 8% a year on average. You estimate a combined federal + state tax rate of 30%.
| Input | Value |
|---|---|
| Shares granted | 500 |
| Current share price | $40.00 |
| Expected annual growth | 8% |
| Vesting period | 4 years |
| Estimated combined tax rate | 30% |
Projected share price after 4 years at 8% annual growth is roughly $54.42, giving a gross value of roughly $27,210. After an estimated $8,163 in income tax (30%) and $2,082 in FICA (7.65%), the estimated net value comes to roughly $16,965 — figures the calculator above will reproduce exactly, including for your own numbers.
US equity compensation — frequently asked questions
Is this the same as the UK Share Incentive Plan calculator above?
No. They model completely different legal schemes with different tax rules. Use the UK calculator only if your employer operates an HMRC-approved Share Incentive Plan; use this one for US-style RSUs, ESPPs, or stock options.
Does this calculator account for my specific state’s tax rules?
No — enter your own estimated combined federal + state rate. State income tax varies widely (some states have none), so this tool intentionally keeps that as a single input you control rather than guessing on your behalf.
What about Incentive Stock Options (ISOs) and the Alternative Minimum Tax (AMT)?
ISOs can trigger AMT on exercise even before you sell, which this simplified tool does not model. If you hold ISOs, this is a starting estimate only — talk to a tax professional before exercising.
Why is FICA not applied to stock options?
Gains from exercising most stock options are generally not subject to FICA in the way RSU and ESPP income is, though the rules differ by option type. This tool reflects that general distinction, not your specific plan’s documentation.
Can I model a graded vesting schedule instead of one lump total?
Not yet — this tool uses a single total vesting period for simplicity. If your shares vest in stages (e.g. 25% per year), you can run the calculator once per tranche using each tranche’s own remaining years.
- IRS Topic No. 427 — Stock Options
- IRS Publication 525 — Taxable and Nontaxable Income (equity compensation)
- Social Security Administration — annual wage base determination
- SEC Investor.gov — Restricted Stock Units and Employee Stock Purchase Plans
Estimates only — not tax, legal, or financial advice. US federal and state tax rules change; confirm current figures with the IRS, your state tax authority, or a qualified tax professional before making decisions.