A pennyweight (abbreviated dwt or denarius weight) is a unit of mass that is equal to 24 grains,  1⁄20 of a troy ounce,  1⁄240 of a troy pound, approximately 0.054857 avoirdupois ounce and exactly 1.55517384 grams.

The pennyweight is the common weight used in the valuation and measurement of precious metals. Jewelers use the pennyweight in calculating the amount and cost of precious metals used in fabricating or casting jewellery. Similarly, dentists and dental labs still use the pennyweight as the measure of precious metals in dental crowns and inlays.

Although the abbreviations are the same, the pennyweight bears no relation to the weight of the American penny nail. That name is derived from the price for a hundred nails in 15th century England: the larger the nail, the higher the cost per hundred. The pennyweight also bears no relation to the weight of the American "penny" (1 cent) coin, which weighs 2.5 g (for those minted after 1982).

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