Equity Compensation Calculator: ISOs, RSUs, and 83(b) Elections in One Tool Suite

If you receive equity compensation — ISOs, RSUs, restricted stock, or stock options — you need more than a spreadsheet to plan your taxes. Different equity types have different tax rules, and the interactions between them can save or cost you tens of thousands of dollars.

EquityTax offers four purpose-built calculators that implement IRS-grade tax logic. Here's what each one does and when to use it.

Which Calculator Should I Use?

Start with your situation to find the right tool:

If you are unsure which situation applies, read through the descriptions below. Most employees use 2-3 of these tools at different stages of their equity lifecycle.

ISO AMT Calculator

What it does: Finds the maximum number of ISOs you can exercise without triggering Alternative Minimum Tax.

When to use it:

• You hold ISOs and want to exercise some this year
• You need to know your AMT-free exercise limit
• You want to compare Conservative, Optimal, and Aggressive exercise strategies

How it works: Implements the IRS Form 6251 AMT calculation and uses binary search to find the exact crossover point where AMT equals your regular tax. Below this point, AMT = $0.

Key outputs:

• AMT-free exercise limit (number of shares)
• Three exercise scenarios with exact tax projections
• Federal and state tax breakdown

For a deep dive on AMT, see our AMT Calculator guide.

RSU Withholding Calculator

What it does: Calculates your actual RSU tax liability and shows the gap between what your employer withholds and what you actually owe.

When to use it:

• RSUs are about to vest and you want to know your true tax bill
• You want to understand the "withholding shortfall" before it surprises you
• You need to plan estimated tax payments

How it works: Applies your actual marginal tax rates (not the flat 22% supplemental rate) to your RSU income, accounting for federal brackets, state tax, and FICA.

Key outputs:

• Total tax owed on RSU income
• Withholding shortfall (what you'll owe at filing)
• Federal, state, and FICA breakdown

Learn more about RSU tax rates and withholding mechanics.

83(b) Election Calculator

What it does: Analyzes whether filing an 83(b) election saves you money on restricted stock or early-exercised options.

When to use it:

• You just received a restricted stock award
• You early-exercised stock options
• You have 30 days to decide and need to see the math

How it works: Compares two scenarios — filing 83(b) (pay tax now at low FMV) vs not filing (pay tax at each vest date at higher FMV). Projects your company's FMV growth and calculates the tax difference.

Key outputs:

• Tax with 83(b) vs without
• Total tax savings from filing
• Filing deadline with automatic countdown
• Urgency level (Green/Yellow/Orange/Red)

Read our complete 83(b) election guide.

IPO Lock-Up Calculator

What it does: Models the tax and liquidity impact of an IPO lock-up period, and compares 5 financing options for covering taxes when you can't sell shares.

When to use it:

• Your company is going public (or recently went public)
• You need to figure out how to pay taxes during the lock-up
• You want to compare SBLOC, PVF, 401(k) loans, and other financing options

How it works: Calculates your total tax liability from vesting events at IPO, identifies the liquidity gap (days between tax due date and lock-up expiration), and models the cost of each financing option.

Key outputs:

• Total tax liability at IPO
• Liquidity gap (days)
• Cost comparison of 5 financing options
• Optimal financing recommendation

See our IPO lock-up period guide and pre-IPO exercise strategies.

The Multi-Year Exercise Planner

All four calculators above handle single-year decisions. But the biggest tax savings come from optimizing across multiple years.

If you hold ISOs alongside other equity, the timing of your exercises over 3-5 years — which years, how many shares, in what order — can save $50,000-$200,000. For timing strategies that coordinate with the multi-year plan, see our guide on when to exercise stock options.

Tax Data and Accuracy

All EquityTax calculators use:

• 2026 federal tax brackets from IRS Revenue Procedures
• IRS Form 6251 logic for AMT calculations
• State-specific rates for CA, NY, WA, TX, and other states
• FICA calculations including Additional Medicare Tax

Our ISO calculator implements the full IRS Form 6251 (Alternative Minimum Tax) computation. It starts with your regular taxable income, adds AMT preference items (the ISO bargain element), applies the AMT exemption ($88,100 for single filers in 2025), and calculates the tentative minimum tax at 26%/28% rates. If the tentative minimum tax exceeds your regular tax, the difference is your AMT liability. A binary search algorithm then finds the exact number of shares where AMT equals $0 — your AMT-free exercise limit.

All tax brackets, exemptions, and phase-out thresholds are sourced from official IRS Revenue Procedures and verified against published Form 6251 instructions. State tax calculations follow each state's official guidance, including California's Mental Health Services Tax (1% above $1M) and New York's supplemental income tax brackets. See the complete 2026 federal tax brackets for reference.

Frequently Asked Questions

Which equity compensation calculator should I use? Start with your equity type. If you hold ISOs, use the ISO AMT Calculator to find your AMT-free exercise limit. For RSUs, the RSU Calculator shows your withholding shortfall. If you received restricted stock or early-exercised options, the 83(b) Election Calculator analyzes whether filing saves money. Around an IPO, the IPO Lock-Up Calculator models your liquidity gap and financing options.

How accurate are online equity tax calculators? Accuracy depends on the underlying tax logic. Our calculators implement the full IRS Form 6251 computation for AMT and use actual 2025 federal and state tax brackets — not simplified estimates or flat-rate approximations. We verify all tax constants against official IRS Revenue Procedures annually. That said, every individual situation has nuances (itemized deductions, other AMT adjustments, local taxes) that a calculator may not capture.

Do I need a CPA or can I use a calculator? A calculator gives you a reliable estimate for planning purposes — it tells you your AMT-free limit, expected tax bill, or withholding shortfall before the numbers are final. A CPA is essential for filing your actual tax return, especially in the year you exercise ISOs or have complex equity events. Use the calculator to prepare and make informed decisions; use the CPA to file accurately.

What data do I need to use an equity calculator? You will need your W-2 income (salary plus bonus), filing status, and state of residence. For ISOs: grant date, strike price, current 409A valuation, and number of vested shares. For RSUs: number of shares vesting and current share price. For 83(b) elections: grant date, current FMV, number of shares, and expected company growth rate.

Can one calculator handle both RSUs and ISOs? RSUs and ISOs have fundamentally different tax treatment. RSUs are taxed as ordinary income at vesting (no choice in timing), while ISOs trigger AMT at exercise (you choose when). Because the tax mechanics differ, we built separate calculators for each. If you hold both, use the ISO calculator for exercise planning and the RSU calculator for withholding planning, then coordinate timing with the Multi-Year Planner.