Broken Tape Measure

I’ve been setting up my new apartment, buying lots of stuff. I have a tape measure I bought in at Tokyu Hands in Tokyo. It turns out it’s wrong. After buying a bunch of blinds and having them not come close to being the correct size I was thinking WTF, false advertising. I was about to take them back when I tried putting on a table cloth I bought and having it also not be the correct size.

So I thought I should go to the store and before I asked to return the stuff I should ask them to check my tape measure. Then it occured to me I could lookup the size of the table which I expected would not be wrong. It’s listed as 86 inches. I checked with my tape measure it says 73 inches. So I check the centimeter size, 220cm. Check the tape measure. 220 CM. I know the conversion is supposed to be 2.54cm to the inch or 100cm (1 meter) is 39.37 inches. I look down at the 100cm mark on the tape measure. It says 33inches. WTF! Now I have to take all this stuff back.

Looking closer at the tape measure the top scale is not inches, it’s in units which are 33 units per meter. Not inches, not metric, must be some old Japanese standard.

  • Very weird! I never heard of that measurement but I found it here:

    It’s called 寸 (sun) and there’s effectively 33 per meter. It must be on that ruler for grandma.

  • Not surprised…

    There’s ton’s of old measurements still used in Japan (e.g. 坪 ,Tsubo being the most common off the top of my head)…

  • Pi

    A quick bit of math shows that the measurements are a ratio of inches to Pi. I recall hearing about this, it’s some sort of tape used by carpenters to measure round logs, to make it easier to determine circumference. It seems to be unique to Japan. I have no idea how it works, it’s been decades since I learned trigonometry.

  • anonymous1

    There’s a Wikipedia entry for the Chinese equivalent, the “cun” (pinyin), which quite frankly seems even more useless with this explanation:

    The cun is a Chinese unit of relative measure that is used to chart acupoints on the human body for accupuncture. The width of a persons thumb at the first knuckle commonly denotes one cun, the width of the two forefingers denotes 1.5 cun, the width of all fingers side-by-side is three cun.

  • anonymous1

    hey greg how about you post something?

  • gaijinhippy

    ten of those “inch size” measurements make one “shaku” which is close to a foot (about 30cm). i used to work in japan as a carpenter and plasterer. a lot of the old carpenters still use this unit of measurement.