The logic of simply summing crimes of all kind into a single total has long been challenged as misleading. All crimes are not created equal. Counting them as if they are fosters distortion of risk assessments, resource allocation, and accountability. To solve this problem, , , and ) has offered a general proposal to create a weighted ‘Crime Harm Index (CHI).’ This article provides and explicates a detailed procedure for operationalizing this idea in UK: what we call the ‘Cambridge CHI.’ The new elements of the Cambridge CHI presented here are (1) the use of the ‘starting point’ in the national Sentencing Guidelines to define the number of days in prison for each offence type; (2) the exclusion of proactively detected, previously unreported offences, and (3) a comparative analysis of the Cambridge and other approaches to weighting crime harm, judged by a three-pronged test of democracy, reliability, and cost.