Palm (unit)

[1] The width of the palm was a traditional unit in Ancient Egypt, Israel, Greece, and Rome and in medieval England, where it was also known as the hand,[2][a] handbreadth,[3] or handsbreadth.

[c] The unit is attested as early as the reign of Djer, third pharaoh of the First Dynasty,[5] and appears on many surviving cubit-rods.

Six made up the "Greek cubit" (meh nedjes) of about 45 cm (1 ft 6 in).

[13] These various palms were divided into four digits (dáktylos) or two "middle phalanges" (kóndylos).

[15] The Roman palm (Latin: palmus) or lesser palm (palmus minor) made up ¼ of the Roman foot (pes), which varied in practice between 29.2–29.7 cm (11.5–11.7 in)[16] but is thought to have been officially 29.6 cm (11.7 in).

[19] The palms of medieval (Latin: palma)[20] and early modern Europe—the Italian, Spanish, and Portuguese palmo and French palme—were based upon the Roman "greater palm", reckoned as a hand's span or length.

The English palm, handbreadth, or handsbreadth is three inches[30][31][32][33] (7.62 cm)[g] or, equivalently, four digits.

[31][h] The palm was excluded from the British Weights and Measures Act 1824 that established the imperial system and is not a standard US customary unit.

A diagram of various units derived from the human hand. The palm (3) was originally the width of the palm but was standardized as the somewhat smaller width of four digits (6). The related shaftment (1) and hand (2) were the width of the palm plus an open or closed thumb. The other units are the span (4) and finger (5).
Detail of the cubit rod in the Museo Egizio of Turin , showing digit, palm, hand and fist lengths
Sign giving the metric equivalents of the units in use in the 17th century in the covered market of Pernes-les-Fontaines in the Vaucluse
The English palm as the width of four fingers.