[1] The term candlepower was originally defined in the United Kingdom, by the Metropolitan Gas Act 1860, as the light produced by a pure spermaceti candle that weighs 1⁄6 pound (76 grams) and burns at a rate of 120 grains per hour (7.8 grams per hour).

At the time the UK established candlepower as a unit, the French standard of light was based on the illumination from a Carcel burner, which defined the illumination that emanates from a lamp burning pure colza oil (obtained from the seed of the plant Brassica campestris) at a defined rate.

It was attended by representatives of the Laboratoire Central de l’Electricité (France), the National Physical Laboratory (UK), the Bureau of Standards (United States), and the Physikalische Technische Reichsanstalt (Germany).

The Germans, however, dissented and decided to use a definition equal to 9/10 of the output of a Hefner lamp.

In general modern use, a candlepower now equates directly (1:1) to the number of candelas[1]—an implicit increase from its old value.