What's My Potential Estate Tax? This calculator helps estimate your federal estate tax liability. You are viewing this website at a small screen resolution which doesn't support calculators. Click here to view this calculator. Share | Related Content When Do You Need a Will? When do you need a will? The answer is easy: Right Now. Put It in a Letter A letter of instruction provides additional and more personal information regarding your estate. Principles of Preserving Wealth How federal estate taxes work, plus estate management documents and tactics.