Abstract: A computer-implemented method of determining particle size and a computer-readable medium storing instructions to execute such a method are presented. The method entails obtaining an image of at least one particle and a calibration mark, wherein the particle and the calibration mark were captured using the same lens, correcting the image for distortion effects to generate a corrected image, wherein the same correction factor is applied to both the particle and the calibration mark, and determining a size of the particle using the corrected image. The method may be useful for obtaining the target size of coffee grounds that will produce the desired flavor. Coffee grounds may be sprinkled on a surface with the calibration mark and imaged with the calibration mark such that the correction factor for the calibration mark can be used to determine the particle size range of the coffee grounds.