Unit Conversion
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This page contains Japanese characters.
Number
hyaku ( ɴ ) = hundred
sen () = thousand
man () = 10 thousand
oku () = 100 million
chou () = trillion
Ratio
han ( Ⱦ ) = 1/2
wari () = 1/10
bu (ʬ) = 1/100
rin () = 1/1000
mou () = 1/10000
The tables shows conversion of Japanese unit[3]. Japanese people usually use man () unit. Man means 10,000. And more it does many simply. Chinese people called international law bankokukouhou ( ˡ ). Japanese people call Chinese Great wall ( ΤĹ ).

We never say it 10 thousand, though we show 3-digit 10,000 in Western style. Japan had used 4-digit division for a long time. Soroban is 4-digit. A gamble trader calls, "chou ( ) ka han ( Ⱦ ) ka", when yakuza films often show dice gamble. Some IJN officers insisted Japan should have 70 % of USN. 70 % is 7 wari ( ) in Japanese. This was big political issue. A few prime ministers were shot to death or injured.
 Length
Length
bu (ʬ) = 1/10 sun = 3.03 mm
sun () = 1/10 shaku = 3.03 cm
shaku () = 30.3 cm
hiro ( ) = ken () = 6() = 1.82m
ri (Τ) = 3.93km
in = 1/12ft = 25.4mm
ft = 30.5cm
yard = 0.914m
mi = 1.61km
nm = 1.85km
Old Japanese people pronounced centi sanchi ( ). Japanese boys were proud of IJN battleship Yamato's 46 cm gun after the Pacific War. But Japanese people did not know Yamato at all. USN did not know that Yamato was more than 60,000t. My father told me how Yamato was big. Yamato was ordered to go to Okinawa as bait for USN carriers' aircraft. The sad operation was the last fleet mission for glorious IJN.

I have known US people use yard. I was surprised that US Army soldiers call ISO meter, when my family watched on US film awarded Academy Prize. My wife said, "US Army depends on foreign soldiers. Foreigners do not know yard." I wonder that US Army changed yard gun sight. The film showed coffins for bodies in a scene. I remember, a TV documentary showed that a medic held a body in bag in US Army hospital in Bagdad. I felt strange. I stopped watching it at once. My wife and son looked it natural. My father told me that IJN Destroyer released bodies in the sea, when I was a boy. The bodies were covered with canvas just after the Leyte Battle. My father was a IJN torpedo sailor.

Hiro ( ) is unit of depth. Some people submerged in the sea and gathered awabi. Awabi is a kind of shell. Okinawa exported awabi to China since Ming. Chinese people likes awabi of Iwate even now. Ken ( ) is the same length of tatami mat of long side edge.

Golf shows yards in Japan now, but Japanese ball parks display ISO meter. IJN aircraft used kt as speed unit. USN and RN and used both kt and mph. IJA used both kt and km/h[1].

 Area
Area
tubo () = 3.3m2
tan (ȿ) = 300 tubo
cho (Į) = 10 tan
in2 = 1/144 ft2 = 6.45cm2
acar = 1/640 mi2 = 40.5a
a = 100 m²
km2 = 100 ha
We count tatami as unit of area especially room in house. We call 1 tatami 1 jyou. So 2 jyou is square of 1 ken. This is a tubo. Tan is unit of farm. 1 tan farm could product rice that a man could live for a year, I suppose. When I knew farm allocation to address in the US, I was very interested. Was it originated since Roman empire?
 Volume
Volume
shou () = 10 gou () = 1.8 L
to () = 10 shou
koku () = 10 to = 180 L[4]
koku () = 10 3 = 278 L (ship, woods)
= kL
in3 = 16.4 mL
gal (US) = 3.78 L
bbl = 42 gal (US) = 159 L
GT = 100 ft3 = 1000/353 m3[2]
Koku was used as scale of local goverment economy. It was amount of rice. For example, Kaga hyaku man goku ( ɴ ). Kaga is also the name of IJN aircraft carrier. It was to a battleship originally. A Japanese drum can contains 200 L. I always saw them in winter, when I was a child. My family bought much coal for heating stove in summer. It was contained at backyard. I do not know when heating fuel was oil. Fuel shop delivered the drum can. I think that there is a regulation not keep much liquid fuel to prevent fire.

IJN destroyers carried oil filled drum cans on their decks, when they depearted from Japan to Pearl Harbor. IJN was anxious about fueling. Destroyers range were short. IJN destroyers carried drum cans filled with rice for IJA soldiers in Guadalcanal. IJN called it Nezumi yusou ( Mouse transport ), though USN called Tokyo Express. The mice actioned at night and ran away at dawn. Ironically USN fighter Wildcat suppressed them at daytime. Although Japanese government use kL of oil unit, market and press use bbl. 20th century was the age of oil and America. It lasts now. Some people proclaim that Japan should grow more food for security. They forget that Japanese agriculture depends oil heavely. Without oil, all the agricultural machines and truks will stop. If the mouth of Persian Gulf shut, Japan will be short of oil in half a year, though Japanese government stocks 1.4 million t of rice. Its stock is 10 kg per person only. Japanese government had rice of a week stock on account of government in the end of the Pacific War.

Engine displacement for RC uses cubic inch even now. caliber of hand gun is also inch. Germany and Japan made 13 mm caliber machine guns. IJN and IJA did not cooperate with standard of machine guns for aircraft. IJA tried to develop deck machine guns for merchant ships. IJN and IJA development of 30 mm guns were rather a commedy.

 Weight
Weight
momme () = 3.75 gf
kin () = 160 momme = 600 gf
kan () = 1000 momme = 3.75 kgf
oz = 1/16lb = 35.3 gf
Momme was also used size of guns since Sengoku era. Local lords worried about buying ammos. The bottle neck of ammos was material of powder. Western traders sold the material of powders and gun much. They got silver or gold from Japan. Without their material, Japan would not able to invade Korea in 16th century.

Kin is the unit of drug trade between UK and Qing. Qing lost much silver for drug. Soon Chinese farmers revolted in short of money. Qing lost her power sharp. Japan did the same like UK in 1930s. She sold drug to Chinese people. Modern drug is electronic game device. Japanese and US companies are sellers for kids. Academy awarded film showed that a soldier played Xbox. My son also plays it very much. Sony or Microsoft study human kids brain and psychology deep. Xbox shows the contamination all over the world in display. US, Western Europe and Japan may lose power in future like Qing. Tired brains do not look into reality and wisdom.

4 1000lb bombs of SBDs hit IJN Kaga at the Midway Battle. While IJN Vals carried a 250kg bomb. 1000lb weighs than twice than 250kg.

[1] Keikiban
[2] Gross ton
[3] Syakan hou
[4] koku


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