How to Find the Scale Length of a Prefab Guitar Neck

Got a guitar neck, but no idea what the scale length is?
If the neck already has frets, figuring it out is simple – and essential for proper bridge placement, especially in DIY builds.
Recently, I published the Fret Calculator tool to get the fret positions on the neck depending on the planned scale length. But when you have the fretted neck, the task is opposite: to figure out the scale length.
It’s especially important to the CBG builders because the cigar boxes have a pretty small size. And not every box will be long enough to accomodate the desired scale length