The measurement of the angle of repose is a conventional method for estimation of powder flowability. This method is known to have lower reproducibility of results when greater angles of repose are obtained, in particular in the case of cohesive powders. The flowability of free-flowable powders can also be characterized by discharging from a hopper. In a cylindrical flat-bottomed hopper having a central circular orifice, a residual amount of powder remains in the hopper at the end of the discharging procedure. In this work, the size fractions of sodium chloride, sodium citrate, and potassium citrate in the range 0.0315-0.0600 cm were characterized with the bulk density and the mass discharge rate through 0.6-1.2cm orifices of the cylindrical stainless steel hopper. The mass of the residual powder has been found to be indirectly proportional to the powder discharge rate. A method of the indirect estimation of the drained angle was proposed. The derived equation uses the mass of the residual powder, the powder bulk density, the inner diameter of the hopper, and the diameter of the hopper orifice as the independent variables. In the studied range of variable values, the experimentally obtained drained angles showed significant negative correlation with the mass discharge rate and the volume discharge rate of test powders, while no correlation was found between the drained angle and the mass discharge coefficient of the Beverloo equation. In order to measure the drained angle in the cylindrical hopper having an inner diameter of 4cm, an orifice diameter equal to 1.0cm was optimal. Filling of the powder into a hopper in conformity with the standard conditions of bulk density measuring in a graduated cylinder is the basic presumption. Since the drained angle follows the relief of bulk powder during discharge from the cylindrical hopper, it thus describes the powder flowability more comprehensively than the angle of repose to the horizontal. Good reproducibility of results follows the 3-D indirect estimation of the drained angle as well. In order to avoid any residue of powders in the conical hopper at the end of the discharging operation, the wall angle could be larger than the drained angle of the powder in the cylindrical hopper. This is typical for the mass flow of size fractions of free-flowable powders, the drained angles of which are approximately two times greater than their angles of repose.