This dataset contains the raw data for the journal article “The influence of porosity on the superconducting properties of Y-Ba-Cu-O single grains”. The file “README.txt” contains detailed information about the measurement of the raw data and the determination of the data shown in the paper. The file “Raw_data.xlsx” contains raw data used to plot the graphs shown in Figures 4, 5, 6(a), 6(b), 7, 9, 11 and 12. The file “1373_25mm_YBCO_tracking_microscope.tif” contains the raw microscope image shown in Figure 3. The zip folders “1A-1H” contain image stacks of sample pieces 1A-1H measured using 3D X-ray Computer Tomography (XCT). Each zip folder also contains a header file with more details about the XCT measurements. The folder “SQUID” contains the raw data used to determine Tc, ΔT90, and Jc measured using a Magnetic Properties Measurement System (MPMS). The folder “Optical_microscope” contains the raw images used to determine the Y-211 particle size and content. Furthermore, it also contains images where the Y-211 particles are marked in green and red, which were used to determine Y-211 size and content.