Coronary stenosis causes alterations in blood flow that influences the pathological process of atherosclerotic disease. The use of computational fluid dynamics has become a strong tool in aiding the diagnosis of coronary atherosclerosis, avoiding more intrusive procedures in patients. In the present work, the velocity and pressure field were determined numerically, using commercial software Fluent, in a section of a coronary. It was investigated possible change in flow pattern, due to several levels of lesions in the coronary arteries. The shear stress was determined on the endothelial wall of the coronary artery and the pressure drop between before and after the obstruction. Satisfactory results were obtained when comparing with experimental data. From the results of the pressure drop pattern in relation to the stenosis level, it was possible to create a fourth order equation for the calculation of FFR (Fractional Flow Reserve) from the area reduction caused by coronary stenosis.