The main aim of this article is to offer a quick and precise predictive method for calculating the daylight factor for different points on the floor of square courtyards under overcast sky conditions. First, the calculation of the predictive method of the sky component is established based on earlier studies and Tregenza algorithms. Subsequently a simulation of the daylight factors on the floor of a courtyard of variable size and reflectance is carried out using two lighting computer programs based on different calculation algorithms. Once the daylight factors are calculated, the reflected component, produced by the reflectance of light on the interior surfaces of the venue, is quantified. Finally, a predictive method of the internally reflected component is established, based on the theory of the integrating sphere. Predictive methods of sky and reflected components are used to determine daylight factors in a courtyard. (C) 2014 Elsevier Ltd. All rights reserved.