The fraction of thermal radiation leaving a surface that is intercepted by another surface. The view factor depends only upon the geometric arrangement of the surfaces, and satisfies the reciprocity relation:

where A_i is surface i and F_ij refers to the fraction of radiation that leaves surface i and is directly intercepted by surface j. The view factor has a numerical value of between 0 and 1. Tables and equations are available for calculating the view factors of some simple and most commonly encountered geometries. It is also known as the configuration factor or shape factor.