what do the british use to measure weight
Stone (unit) The stone remains widely used in the UK and Ireland for human body weight: in those countries people may commonly be said to weigh, e.g., "11 stone 4" (11 stones and 4 pounds), rather than "72 kilograms" as in many other countries, or "158 pounds" (the conventional way of expressing the same weight in the US).[38] The correct plural form of stone in this context is stone (as in, "11 stone" or "12 stone 6 pounds"); in other contexts, the correct plural is stones (as in, "Please enter your weight in stones and pounds"). In Australia and New Zealand, metrication has almost entirely displaced stone and pounds since the 1970s.
Pound (mass) The libra (Latin for "scales / balance") is an ancient Roman unit of mass that was equivalent to approximately 328.9 grams.[15][16][17] It was divided into 12 unciae (singular: uncia), or ounces. The libra is the origin of the abbreviation for pound, "lb".