Metric vs Imperial Weight: A Complete Comparison

The metric system uses the kilogram (kg) as the base unit of mass — it is one of the seven SI base units. The kilogram is subdivided into grams (1 kg = 1,000 g) and further into milligrams (1 g = 1,000 mg). Larger weights use metric tonnes: 1 metric tonne = 1,000 kg. The system is completely coherent: every unit is a factor of 10 away from adjacent units.

Common metric weight anchors: a typical adult male weighs 70–80 kg; a standard bag of flour is 1 kg; a standard international airline checked bag limit is 23 kg (about 50.7 lb). In cooking, precise baking uses grams; grocery shopping in most countries uses kilograms. Pharmaceutical dosing uses milligrams and micrograms.

The US customary system uses the avoirdupois pound (lb) as its primary weight unit: 1 lb = 16 ounces (oz) = 0.453592 kg. Larger weights use the short ton (US ton = 2,000 lb). The UK and some Commonwealth countries historically used the long ton (2,240 lb) and stone (14 lb). The imperial system is not a coherent system — its unit relationships are arbitrary historical survivals rather than designed ratios.

Common US weight anchors: the standard checked baggage limit is 50 lb (22.7 kg); a US gallon of water weighs about 8.34 lb (3.78 kg); a typical adult male in the US weighs 170–200 lb. Food packaging in the US shows weight in oz and lb; many products show both oz and grams for the international market.