Scan-a-nozzle (flatbed scanner stand for E3D/Prusa/original Anet nozzles)

thingiverse

You can place four nozzles face-down on a flatbed scanner and get an approximate diameter reading using pixel measurement. To calculate the size in millimeters, multiply the size in pixels by 25.4, then divide by the DPI of your actual scan settings. Keep in mind that this is a rough estimate and not suitable for calibration purposes. However, it can help you determine if unusual filaments like wood, metal, carbon fiber, glitter, or sand are expanding the nozzle opening more than expected. For this method to be effective, you'll need a scanner with at least 600 DPI resolution. If you want to avoid losing nozzles during removal, increase the horizontal expansion by 0.1-0.2mm. I made this adjustment in my previous nozzle holder design to prevent annoying difficulties when removing nozzles.