Study air infiltration into the building in several ways such as energy, air quality, thermal comfort and pollution entering in the building is very important. In this context, many studies have been conducted in different countries. In our country due to the use of steel doors and windows, do independent research on the gap size and air infiltration is necessary .In this study, by practical view and in order to localize results, based on a field study, the actual dimensions of the gaps around conventional doors and windows in Iran is measured. The results of these measurements are used to simulate gaps, then with experimental study, air infiltration rate of this gaps is calculated at different pressures. In present study, after investigating the effect of different aspects of gaps on air infiltration rate, two common equations, power law and quadratic equation, in order to fitting data were compared. Results show that power law equation can adapt better to the experimental data. Coefficients of the power law equation to estimate the air infiltration rate through the gaps was presented. By analysis of the results, due to the proximity factor of the pressure difference to the number 0.5 in most of the results, it was concluded that the Bernoulli equation can be used to predict the air infiltration rate through the gaps. This equation is better compliance with laws and physical principles. Discharge coefficient of the Bernoulli equation for gaps with different dimensions are calculated.