Convert pounds to kilograms

Shopping in US stores, following an Anglo-American diet or reading the weight of an imported product all mean turning pounds into kilos.

The pounds are multiplied by 0.45359237. Because the factor is an exact definition, no precision is lost in the conversion.

Where you will meet pounds

Checked baggage on American airlines, shipping weights in US shops, gym plates, British and American recipes, and body weight in American medical records. In all of these the figure has to be translated before comparing it with anything metric.

Baggage is the costliest case

Many airlines set the limit at 50 pounds, which is 22.7 kg, not 23. The three-hundred-gram difference seems irrelevant until the check-in scale reads just over and you pay an excess fee. When the limit is announced in kilos it is usually 23, slightly more generous.

Gym weights

An American 45-pound plate is 20.4 kg, while the equivalent metric plate weighs exactly 20 kg. A 45-pound Olympic bar is 20.4 kg against 20 kg for the metric one. When comparing lifts between gyms, the difference accumulates with every plate.

In the kitchen, weigh rather than convert

A pound of flour is 453 grams, but English-language recipes usually measure in cups, which are volume rather than weight. Converting cups to grams depends on the ingredient: a cup of flour and a cup of sugar do not weigh the same.