You will rarely find a definitive final number for two reasons:
A cleaned version containing only English-language titles and removing duplicates (e.g., version 1.1 vs. 1.2) significantly reduces the size to roughly 652 GB . 3ds Complete Rom Set Size
The Nintendo 3DS had a vast library of games, with over 1,100 games available during its lifespan. The size of these games can range from a few megabytes to several gigabytes. For instance: You will rarely find a definitive final number