Abstract The inner volume of a 1000L bell prover is measured by a new facility. A chord length measuring element is made up of two length gauges and a rotating arm. The whole volume of the bell is measured off 256 cross sections with axially equal spacing, and the spatial coordinates of the points, at which length gauges contact the bell’s inner wall,are obtained with a sampling interval of 15° to reproduce every section profile. A new sweep method is introduced to calculate the areas of section profiles. The comparison with the method for the assessment of departure from roundness shows that the results of the two methods coincide with each other when small sampling interval is adopted. A data sheet for all element volumes along bell axial is presented as calibration result.