Pounds to Stones Converter

Mass is measured against the kilogram, the SI base unit. Every unit here is stored as its exact number of kilograms, so a conversion is simply the input turned into kilograms and then into the target unit. The metric prefixes run the full modern range on the gram — from the quecto­gram (10⁻³³ kg) to the quetta­gram (10²⁷ kg), including the ronna and quetta prefixes added in 2022. The everyday imperial and US units are avoirdupois, where a pound is exactly 0.45359237 kg and splits into 16 ounces; precious metals use the troy system, where a troy ounce (31.10 g) is heavier than an avoirdupois ounce (28.35 g); gemstones use the metric carat (0.2 g); and the apothecary system survives in scruples and drachms. Regional and historical units — the tola, tael, catty, pood and physics’ slug — sit alongside scientific masses like the dalton, electron and Planck mass, and astronomical masses from the lunar mass up to the solar mass. Strictly these are units of mass; on Earth an object’s weight is proportional to its mass, so in everyday use the two are converted the same way.