Military casualties are the common metric of war. Every war leads to losses, now, in the past, and in the future. And in each case, people are losing fathers, sons, mothers, and daughters and countries are sacrificing their most committed citizens. Each individual has a personal experience with war and these experiences drive the formulations of their wartime views. If the costs are perceived to be too high, the citizen ends his or her support for the conflict. If the costs are modest and the goal is important, the citizen remains supportive of the policy. Individuals are uncertain what the total costs of any particular conflict are until the conflict is over. But citizens are called upon to make ex ante judgments about a policy before the data are clear, even before a conflict starts. In order to make those assessments, they have to estimate what they think obtaining the war’s objectives will cost, in human terms using casualty characteristics that include their accumulation, recency, and trend as well as their spatial distribution and social connections. In the end, Costly Calculations are personal assessments by individuals about a war’s value and costs.