This page describes an obsolete unit.

The unit described on this page was in use prior to modern methods of precision measurement. It was based on a standard which is no longer available, and which is not capable of being calibrated against modern measurement units. Therefore, the equivalence to modern SI units or to current United States customary units can only be considered approximate.

The perche (sometimes rendered perch in English) was a subsidiary unit of length in the French pre-revolutionary system, defined as 3 toises. Its value varied from place to place within France, but the values used in Paris are generally taken as the standards in reading older literature. (Note that the term perche was also used for a unit of area.)

Value in terms of modern unitsEdit

Based upon the value of 1.9490365 m for the toise, the legal equivalence at the time the metric system was adopted in France, the length of the perche was 5.8471095 m = 6.394476706036745 yd.

Relation to other French pre-revolutionary length unitsEdit

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