IFRS will be truly global when the US adopts, but there are principled objections to IFRS in the US debate. There is a wealth of information about verbal differences between the standards, but little about the monetary significance of the differences. We measure the differences, and show how they influence investors, financial analysts, and academic researchers. There are important monetary differences in balance sheets, income statements and cash flow statements. The differences are important on an average, on a line-item, and on a firm-level basis. Important as are the differences, they arise mainly from only a handful of differences that matter.