I love the videos of Black Magic Craft and have often rebuilt something. Among them were also times dungeon tiles, which I then measured with ruler and angle. Since I start in the next few weeks a new project for which I need dungeon tiles, I have created a model in Freecad. I'm too lazy to have to measure every time something new and can now simply put the blank tile on the foam and trace. So I can work faster and can save time when measuring. I'd rather spend more time tinkering and trying things out and not be held back by repetitive tasks.
Since Jeremy has mentioned so many times that a dungeon tile has to be exactly 3", my brain has stored that as "1 Jeremy". So 1J is 3" or 76.3mm.