How do I estimate whether exercising my ISOs will trigger AMT this year?

When you exercise incentive stock options and hold the shares past year-end, the 'bargain element' (fair market value at exercise minus your strike price) is added back as income for AMT purposes even though you haven't sold. If that add-back is large relative to your income, you may owe AMT. A rough approach: estimate the total bargain element, add it to your other AMT income, subtract the AMT exemption (which phases out at high income and is set annually by the IRS), and compare the resulting AMT to your regular tax. Many people exercise just enough shares each year to stay under the AMT crossover point, spreading exercises over multiple years. You may later recover AMT paid via the minimum tax credit. Given the complexity, model it with tax software or a CPA before exercising.