What aims should guide a new constitution’s drafters? Aspirational homilies about the rule of law, human rights, or democracy aside, there remains a surprising dearth of tools with which to gauge the success or failure of a constitution. We suggest four mid-range metrics for constitution-making: the legitimation of a new state; the channeling of political conflict; the dampening of agency costs from representational government; and the creation of national public goods. We apply these metrics to the 2004 Afghan constitution, arguing that it has had some modest successes in some areas, while failing in others.