Stock Options Evaluator
Estimate the value and tax impact of ISOs and NSOs, including AMT exposure, FICA, NIIT, and exercise scenario comparisons.
Stock Options Basics
Stock options give you the right to purchase shares of your company's stock at a predetermined price (the strike price or exercise price). If the stock price rises above your strike price, the difference -- called the spread -- represents your potential gain. Unlike RSUs, options require you to pay the exercise cost out of pocket, and they can expire worthless if the stock price never exceeds the strike price.
The two most common types of employee stock options are Incentive Stock Options (ISOs) and Non-Qualified Stock Options (NSOs). They differ significantly in their tax treatment, which can have a substantial impact on your net proceeds.
ISO vs NSO Tax Treatment
Non-Qualified Stock Options (NSOs) are straightforward from a tax perspective. When you exercise NSOs, the spread between the fair market value and the strike price is taxed as ordinary income. This means federal income tax, FICA taxes (Social Security and Medicare), and state income tax all apply at exercise. Any subsequent gain or loss from holding the shares is treated as a capital gain or loss.
Incentive Stock Options (ISOs) receive preferential tax treatment under certain conditions. If you hold the shares for at least one year after exercise and two years after the grant date (a qualifying disposition), the entire gain from strike price to sale price is taxed at long-term capital gains rates. No ordinary income tax or FICA applies. However, the spread at exercise is an adjustment item for the Alternative Minimum Tax (AMT), which can create a significant tax liability at exercise.
If you sell ISO shares before meeting the holding period requirements (a disqualifying disposition), the tax benefit is partially lost. The lesser of the spread at exercise or the total gain becomes ordinary income, though importantly, this income is still exempt from FICA taxes.
Understanding AMT on ISOs
The Alternative Minimum Tax is a parallel tax system designed to ensure taxpayers with significant deductions or preferential income still pay a minimum level of tax. For ISO holders, the spread at exercise is added to your income when computing AMT, even though it is not taxed under the regular tax system.
AMT is calculated by starting with your Alternative Minimum Taxable Income (AMTI), subtracting an exemption amount (which phases out at higher income levels), and applying AMT rates of 26% and 28%. You owe AMT only if the tentative minimum tax exceeds your regular tax liability. The AMT paid on ISO exercises may be recoverable in future years as an AMT credit when you eventually sell the shares, but the timing mismatch can create cash flow challenges.
Exercise Strategies
Exercise and sell (same-day sale): The simplest approach. You exercise options and immediately sell the shares, locking in the spread as your profit. This eliminates stock price risk but forgoes any potential future appreciation. For ISOs, this is a disqualifying disposition.
Exercise and hold (short-term): You exercise and hold shares for less than one year. This exposes you to stock price risk. For NSOs, any gain above the exercise FMV is taxed at short-term capital gains rates (same as ordinary income). For ISOs, selling before the holding period creates a disqualifying disposition.
Exercise and hold (long-term): You exercise and hold shares for one year or more. For NSOs, any gain above the exercise FMV qualifies for long-term capital gains rates. For ISOs, if you also meet the two-year-from-grant requirement, the entire gain from strike to sale price is taxed at long-term capital gains rates -- the most favorable treatment. However, you bear stock price risk for the holding period and may owe AMT at exercise.
Key Considerations
The decision of when and how to exercise stock options depends on several factors: your risk tolerance, cash available for exercise, expected stock price trajectory, your overall tax situation, how the grant fits into your compensation package, and how close the options are to expiration. For ISOs in particular, the AMT implications can be substantial and may require careful planning across multiple tax years.
Some states, including California, New Jersey, and Minnesota, do not conform to the federal ISO tax treatment and tax the spread at exercise as ordinary income for state purposes. This calculator includes a toggle for this state-level treatment. If you are comparing multiple packages, the Job Offer Comparison Tool can help place the option grant in the context of salary, benefits, and location.
Limitations and Disclaimers
This calculator provides estimates based on 2025 federal tax brackets and simplified assumptions. It does not model AMT credit carryforward, which can offset future tax liabilities when ISO shares are sold. The ISO $100,000 annual exercise limit is not enforced. State capital gains taxes use the same flat rate as ordinary income, which may differ from actual state treatment. Standard deduction is assumed for all filers. FICA calculations assume exercise as a current employee; post-separation exercises may not be subject to FICA. Capital loss limitations ($3,000 per year against ordinary income) are not modeled. For significant stock option exercises, work with a qualified tax advisor who can account for your complete financial picture.