The force factor method has garnered much attention and application in police use-of-force research, but the reliability of the method has yet to be intensively studied. Using official reports from the Seattle Police Department during a two-and-a-quarter-year period (n = 1,240), officer–suspect interactions were coded from the content of report narratives. Static force factors compared the maximum force applied by the officer with the maximum level of suspect resistance. Dynamic force factors were also recorded, including up to 10 iterations of dyadic action/reaction coded using the same coding scheme. The coding of force factors was completed independently by two teams working at different institutions in a fully crossed design. Evidence on the interrater reliability and subsequent utility of force factors is presented and discussed. Results indicate acceptable levels of agreement across coding teams and support the use of force factors as a central tool for studying asymmetrical social encounters and the proportionality of force.