The rate of energy transfer between compactor and compacted soil is directly related to compaction effectiveness. In this study, a vibrating plate compactor and a rammer compactor were instrumented to determine contact forces and energy transfer rates. The compactor energy measurements and the corresponding unit weight measurements of the compacted soil were in good agreement with the results of conventional laboratory compaction tests. Consequently, it is possible to determine the amount of operating time required for these compactors to impart a particular compactive effort to a lift of soil of known volume. It was found that a Wacker BPU2440A vibrating plate compactor imparts the standard Proctor (ASTM D 698) compactive effort to one cubic meter of soil in about 18 minutes and a Wacker BS60Y rammer compactor imparts the standard Proctor compactive effort to one cubic meter of soil in about 12 1/2 minutes. Such knowledge may be useful in contractors' estimates of construction costs and, as an adjunct to unit weight measurements, in quality control and quality assurance programs.