This study focuses on the oil flow, supplied from the oil hole in plain bearings; the oil flow in bearings that were statically loaded was measured precisely using a test rig. In the case that oil was supplied through an oil hole, experimental results showed that the bearing oil flow depended largely on the circumferential angle of the oil feed hole in relation to the loading direction. When compared with the results of conventional theoretical analysis, it became obvious that the conventional analysis method could not make an exact prediction.The authors have assumed that such difference would come from the oil film extent. Using a transparent bearing so that the behavior of the oil film within the bearing clearance could be visible, the oil film extent for different circumferential positions of the oil feed hole were observed. The bearing oil flow was calculated based on the actually measured oil film extent. The calculated result was compared with the experimental one. The results have shown that the measured value agreed with the theoretical value relatively well.Also, the effects of the bearing operating parameters such as oil supply pressure, revolution of the shaft, bearing load and oil inlet temperature were studied in relation with the bearing oil flow and the oil film extent with the same method.As a result, it has been clarified that the bearing oil flow is largely influenced by the oil film extent and that the knowledge of the exact oil film extent is extremely important for the prediction of bearing oil flow.