Amyloid fibrils are characterized by pitch length and height. Fibril pitch is analyzed from fibril height profiles along the fibril length extracted using Gwyddion. Multiple pixel averages have been used to measure slightly curved fibrils. This is acceptable for analysis since the absolute height of the fibrils does not influence pitch analysis. Additionally, length profiles shorter than 300 nm are excluded from the analysis. The Fourier transforms of the fibril height profiles were computed, using the fft and fftfreq modules of the scipy.fft python library. To avoid the frequency domain being dominated by measurement noise and the mean fibril profile, frequencies translating to length scales below 5 pixellengths and above 1/3 of the full fibril or profile length are excluded. From the remaining frequency domain, the primary frequency peak is identified as the frequency of fibril rotation and converted to length to obtain the periodicity. The pitch length (full 360 degree rotation) is calculated as double the length of a single fibril rotation. Fibril height is analyzed from fibril cross-section profiles extracted using Gwyddion. The surface baseline is calculated as the median height of the cross-section and fibril height is calculated from the peak of the cross-section.