Weight / Mass Converter

This converter handles weight and mass across metric units (milligrams through metric tons) and imperial/US customary units (ounces, pounds, stone, and US short tons), converting through kilograms as the common base unit.

The most commonly searched conversion — kilograms to pounds — uses the exact factor 1 kg = 2.20462262185 lb, defined precisely since the international pound was standardized in 1959 as exactly 0.45359237 kilograms. A 70 kg person weighs 70 × 2.20462 ≈ 154.3 lb.

Stone is a unit mostly unfamiliar outside the UK and Ireland, where body weight is still commonly expressed in stone rather than pounds or kilograms: 1 stone equals exactly 14 pounds, so a person weighing 154 lb is 11 stone exactly (154 ÷ 14 = 11), or more precisely 11 stone 0 lb — often written as "11st" or "11 stone."

Technically, weight and mass are different physical quantities — mass is an intrinsic amount of matter, while weight is the force gravity exerts on that mass, and would change on the Moon even though mass wouldn't. In everyday use (and in this calculator), the two terms are used interchangeably, since on Earth's surface they're proportional and the distinction rarely matters outside physics.

Metric tons (1,000 kg) and US short tons (2,000 lb, roughly 907 kg) are close but not identical — mixing them up in a shipping, freight, or industrial context can create a meaningful error, so it's worth double-checking which "ton" a source is actually using before converting.

Not every "ounce" is the same, either: this converter uses the standard avoirdupois ounce (1/16 of an avoirdupois pound) used for everyday goods. Precious metals like gold and silver are instead measured in troy ounces, a different and slightly heavier unit (about 31.1 grams versus 28.35 grams for a standard ounce) — a distinction worth knowing if you're ever converting jewelry, bullion, or other precious metal weights.