Pennyweight

Pennyweight
17th-century Irish weight, 8 dwt
General information
Unit systemTroy weight
Unit ofMass
Symboldwt
Conversions
1 dwt in ...... is equal to ...
   Troy   1⁄240 troy pound
   Avoirdupois   0.05485714 oz
   SI units   1.555174 g
Irish gold pistole, bearing its weight (4 dwt 7 gr) (National Museum of Ireland – Decorative Arts and History)

A pennyweight (dwt) is a unit of mass equal to 24 grains, 1⁄20 of a troy ounce, 1⁄240 of a troy pound, approximately 0.054857 avoirdupois ounce[1] and exactly 1.55517384 grams.[2] It is abbreviated dwt, d standing for denarius – (an ancient Roman coin), and later used as the symbol of an old British penny (see £sd).

  1. ^ Calculated using the relationships:
    1 avoirdupois ounce = 437.50 grains,
    1 troy ounce = 480 grains.
  2. ^ Calculated using the relationship
    1 troy grain = 0.06479891 gram (exact by definition).