The computations focus on the cost of a year in prison, the average number of crimes committed in a year by typical prison-bound offenders, and the average cost of a crime to society. Prison costs include custodial costs, the amortized cost of prison construction, and the indirect cost of removing an offender from the community. The estimate of crime costs is derived from a review of published crime costs converted to 1983 dollars. Annual offender rates are obtained from a Rand Corporation study of 2,190 inmates confined in jails and prisons in California, Michigan, and Texas. The study computes the crime costs saved per year by incapacitating habitual offenders. The study concludes that even in compensating for estimate errors by doubling the computed annual confinement cost, halving the average crimes per offender, and halving the average cost per crime, $50 million in confinement investments would avert $107 million in social costs. Studies also suggest that the certainty of imprisonment deters crime. 2 figures, 2 tables, and 13 references.