Computational interface for the determination of optimal tilt angle for solar photovoltaic systems in selected locations in Nigeria was developed, and result validated by comparison with similar package such as Photovoltaic Geographic Information System (PVGIS). Monthly clearness index values for each selected cities in the six regions of Nigeria were used as representative clearness index to generate the optimal tilt angles for geographical regions in Nigeria. The yearly angle of tilt of a solar panel installed in any region in Nigeria is approximately equal to the latitude of the region.