Measuring GPU length and thickness
Fit failures are mechanical. Specs lie when you measure the wrong endpoints.
Length
Measure the card the way the case manual defines GPU max length. Include the I/O bracket plane to the far end of the cooler/backplate as your case vendor requires.
Thickness / slots
Count how many motherboard slots the cooler blocks. A 3.5-slot card can kill the slot below even when length fits.
Third dimension: cables
Modern power connectors stick out the side. Cases with vertical mounts or tight glass can fail even when the spreadsheet says OK.
General information, not personalized advice.