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 diedo (meaning digit or finger) was a unit of length or distance in the old Castilian system of units. Since no actual Castilian standards are definitively known by the present day, the only way of determining the length of any Old Castilian unit would be to measure something in modern terms whose length was given by the Castilians in their units. And because this procedure does not give us any clue to which unit may have been the base unit and which were subsidiary units, this distinction really does not apply to the Old Castilian units here given, so all the units really have equal status. However, most references appear to have treated the vara (Castilian yard) as the base unit, expressing other units in terms of the vara.

Value in terms of the varaEdit

The diedo was equal to 1/48 vara.

Relation to other Old Castilian unitsEdit

  • According to Cardarelli[1]:
    • 12 lineas (Old Castilian lines) = 1 diedo
    • 6 diedos = 1 coto
    • 8 diedos = 1 sesma
  • According to Woolhouse[2]:
    • 9 lineas = 1 dedo (so spelled in Woolhouse's tabulation)

Value in terms of modern unitsEdit

Based on the figure of 0.835905 m for the length of the vara, given by Cardarelli in his tabulation[1], the diedo was 0.0174147 m = 0.685618 in. Other values of the vara[3] have been found in the literature as well, differing slightly from Cardarelli's, which would lead to slightly different values for the length of the diedo.

In Woolhouse's table[2], the unit is spelled dedo, and its value is given as 0.6955 in (1.7666 cm).


  1. Cardarelli, François (1998). Scientific Unit Conversion. Berlin, Heidelberg, New York: Springer-Verlag. ISBN 3-540-76022-9. 
  2. Woolhouse, Wesley Stoker Barker (1864). London, England: Virtue Brothers & Co. (Reprinted by Kessinger Publishing). 
  3. The variable vara (length of the vara in Spain and various former colonies)
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