Weight Converter

The International System of Units (SI) defines the kilogram as the base unit of mass. Until 2019, the kilogram was defined by a physical platinum-iridium prototype kept in Sèvres, France – the only SI base unit still based on an artifact. Since 2019, the kilogram has been defined exactly via the Planck constant, ensuring an unchanging and universally reproducible definition. Metric units: 1 t = 1,000 kg = 1,000,000 g = 1,000,000,000 mg.

In everyday life we encounter two different pound definitions: the English pound (lb, avoirdupois pound) = 453.592 g is the international standard in sports, medicine and trade. The German pound (Pfd, 500-gram pound) = 500 g is common in German grocery stores, recipes and everyday language. "Half a kilo" and "a pound" are synonymous terms in Germany. This risk of confusion is especially relevant for fitness apps and body weight figures: if a US app shows "150 lb", that is about 68 kg – not 75 kg, as the German pound would suggest.

In the jewelry and gemstone industry, carat (ct) is used as a unit of weight: 1 ct = 0.2 g. The carat historically derives from the seed of the carob tree (Ceratonia siliqua), whose seeds have an almost constant weight of about 0.2 g. It should not be confused with gold karat (kt), which indicates the purity of gold in parts of 24 (24-karat gold = pure gold, 18-karat gold = 75% gold content).

In international trade and freight transport, the correct conversion of tons plays an important role. The metric tonne (1,000 kg) is the German standard, while in English-speaking countries the short ton (2,000 lb ≈ 907 kg) and the long ton (2,240 lb ≈ 1,016 kg) are common. When it comes to shipping loads and commodity prices, these differences can have significant economic effects. In pharmacy and chemistry, milligrams and micrograms are also used for drug dosages – 1 mg = 0.001 g, 1 µg = 0.000001 g.

Typical conversion errors arise when people use "pound" without specifying which one: in a German recipe, "500 g flour (1 pound)" means the 500-gram pound, while a US nutrition label with "1 lb" always means the English pound (453.6 g). Our converter clearly separates both pound variants and helps avoid this common source of error in everyday life.