This paper considers the relationship between fines for cartels and generalised harm or corporate benefit, showing that the deterrent effect of fines is based on their relationship to corporate benefit. It also considers how knowing the amount of harm or corporate benefit can help to ensure appropriate fines and identifies different methods for calculating harm and corporate benefits related to individual cartel cases. This was prepared as background material for the session "Cartels: Estimation of Harm in Public Enforcement Actions" held at the 2017 Latin American and Caribbean Competition Forum in Nicaragua on 4-5 April 2017.