Abrasive wear of the orifice cannot be avoided for a hopper which should be operated uninterruptedly for a long time in engineering applications. Consequently, the change of the orifice shape will lead to the variation of flow rate for the hopper. In this paper, the influence of orifice shape on the flow rate in ordinary flat-bottom hoppers is investigated both numerically and experimentally. The flow rate increases when the orifice is from sharp to smooth in both flat-bottom and conical-bottom hoppers. The data can be well fitted with a modified Beverloo's formula. The result is supported by the profile of kinetic pressure near the orifice. Moreover, the fluctuation of the instantaneous flow rate is reduced with smooth orifice. In addition, it is found that the diameter of the hopper D and the thickness of the bottom H do not influence the flow rate. This paper contributes to control the flow rate by optimizing the shape of orifice. Display omitted •The first investigation of the influence of the orifice shape on the flow rates in a hopper•Both experimental and numerical studies are performed to explain this phenomenon.•The increasing of radius of the arc on the orifice reduces the empty annulus.