What is a "circular error probable" (CEP)?

A "circular error probable" (CEP) is a statistical measure used to indicate the accuracy of munitions delivery. It specifically represents the radius of a circle within which a certain percentage of rounds will fall when fired at a target. The most common threshold used in determining the CEP is the 50% probability (also referred to as the 50% CEP), meaning that if a munitions system has a CEP of 100 meters, 50% of the rounds are expected to land within that 100-meter radius of the intended target point.

This concept is essential in military operations as it helps command and control personnel assess the effectiveness and reliability of various weapon systems. Understanding CEP allows planners to make informed decisions regarding targeting, risk analysis, and operational tactics, ensuring that they can achieve the desired effects while minimizing collateral damage.