You may have seen the word shaku before, or maybe sun or bu whilst perusing swords on the internet. These terms aren't however exclusive to the japanese sword, they are units of measurement which strangely enough coincide quite closely with our own feet and inches. There will be people who will groan at that because it's a gross over generalisation, but at least for Shaku and Sun, you can imagine a length in your head by simply swapping those values for feet and inches. 1 Shaku is roughly 11.9 inches and 1 Sun is around 1.2 so you can see what I'm getting at.
|Shaku||- 11.93 Inches||- 30.3022 cm|
|Sun||- 1.193 Inches||- 3.03022 cm|
|Bu||- 0.1193 Inches||- 3.03022 mm|
|Rin||- 0.01193 Inches||- 0.303022|
As a cutter, I don't really need to get into the exact measurements but it is useful to know. Collectors of antique and true nihonto on the other hand know these measurements off by heart and you won't see anywhere that sells these swords having labelled them up in metres.
Hopefully with that little rule of thumb, as long as you remember it's not entirely accurate, should help you visualise the different lengths as you see them written.