That's a really nice tool, well thought-out, and the calculations it does are spot on. However, I think it's based on one pretty big assumption: that the shares that investors buy are the same as the shares that you would get through your ISOs. They typically are not the same, with the investors getting preferred shares that are superior to your common shares. Furthermore, terms like liquidation preferences and "participation" can make the preferred shares much much more valuable in many types of liquidity events. So in all, I worry that this tool does more harm than good. Even given all the information you solicit from the user it is still very hard to say what the options/shares are worth. Typical errors in the estimate could be an order of magnitude or more.