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New U.S. Customary Units

Topino 106
Countries where the SI is not the unique or principal system of measurement are marked red. Source: wikipedia.

In 2019 the SI underwent a major revision which completely eliminated reference physical objects and defined all units as rational multiples of measurable fundamental constants.

U.S. new year resolution: modernize as well its own set of units by adding the following definitions.

Curve Foot

The curve foot, symbol cft, is defined such that the circumference with diameter 1 ft is 3 cft long, i.e. $1\,\mathrm{cft} = \frac{\pi}{3} \times 1\,\mathrm{ft}$.

Engineers think 10 % faster when using the curve foot for trigonometry.


The chaincup, symbol C-cup, is a unit of mass defined as the average mass of a standard 1×7/16” stainless steel chain cut short to the maximum integer number of links that allows to fill a standard cooking cup without crossing the circle delimited by the top border.

Troy hundredweight

The troy hundredweight, symbol thun, is a unit of time defined as the time it takes a 5 feet, 1 short hundredweight troy-weight-user goldsmith to complete a 220 yards fall down to sea level at 1 troy atm, 40 % relative humidity and 25 troy degrees.


The furshort, symbol fsh, is a FORTRAN SHELL unit of length defined as the absolute value average of the polar equinoctial projection of the principal axes of the hairs of the fur on the back of a median 2 3/16 pounds ferret (Mustela putorius furo) in springtime in the “Euler-symmetrized” frame of reference of the head of the ferret (Mustela putorius furo) when it’s eating.

Auxiliary Ounce

The auxiliary ounce, symbol aoz, is defined as 234/235 of an ounce. Use it when you run out of ounces. It is smaller than the regular ounce for historical biasing reasons.

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