Free convection heat transfer in enclosures was previously studied for specific operating, geometric and orientations conditions. A lot of correlations are presented in the literature for specific conditions. The current work aims to do inclusive experiments of heat transfer in heated enclosures for different inclination angles, venting configurations, venting opening ratios and Rayleigh numbers. Three various configurations of enclosure openings for air venting were examined: (i) top openings, (ii) side openings, and (iii) top and side openings. The experiments were conducted for wide ranges of venting opening ratios, inclination angles and Rayleigh numbers for each configuration of air venting. Developed correlation was presented for the studied venting configurations to expect the enclosure Nusselt number in terms of Rayleigh number, opening ratio, enclosure inclination angle and openings arrangements. It was found that the developed correlations can predicts the present experimental and previous results within ±8% error. The results showed that for all the studied venting configurations, the Nusselt number enhances with increasing the Rayleigh number, vents opening ratio and in range from 0° to 90° enclosure inclination angle. Furthermore, the top and side openings configuration showed the greatest Nusselt number.