Presidents' unilateral sway over policy is of global concern to scholars, practitioners and the general public. While pending actions provoke media speculation about how much authority presidents have to change policy without legislatures, scholarship has yet to systematically measure presidential discretion across areas of public policy. This study surveys an interdisciplinary panel of scholars, using discrete choice experiments to estimate the latent level of discretion that US presidents have in fifty-four policy areas. Consistent with models of delegation and unilateralism, these measures confirm that presidents have more discretion in foreign affairs, and that discretion promotes executive action. This approach presents the opportunity to examine differences in presidential discretion and public perceptions of presidential power, and can be applied beyond the US case.