There are two types of 'typical option plans': statutory and non-statutory. Exercising a statutory option plan doesn't incur a taxable benefit until the actual stocks are sold, which may be a different tax year. There's a decent summary of it at irs.gov: http://www.irs.gov/taxtopics/tc427.html
You might want to include a reference to it, since it appears that your calculator is based on the exercise triggering a tax event. Exercising may not always trigger a tax event.
There are two types of 'typical option plans': statutory and non-statutory. Exercising a statutory option plan doesn't incur a taxable benefit until the actual stocks are sold, which may be a different tax year. There's a decent summary of it at irs.gov: http://www.irs.gov/taxtopics/tc427.html
You might want to include a reference to it, since it appears that your calculator is based on the exercise triggering a tax event. Exercising may not always trigger a tax event.