Weight Conversion Matrix

Weight (technically mass) measures the amount of matter in an object. The international base unit is the kilogram, redefined in May 2019 by fixing the numerical value of Planck's constant — replacing the previous physical artifact (Le Grand K). This converter covers the full range of mass units: SI standard (kilogram, gram, milligram, microgram, metric ton), American customary (pound, ounce, US ton, grain), British imperial (stone, UK long ton), and specialty units (carat for gemstones). Each conversion follows precise 1959 international definitions: 1 pound = exactly 0.45359237 kg, 1 ounce = 28.349523125 g. Use mass conversion for body weight, food and cooking, shipping and freight, jewelry and precious metals, pharmaceutical dosing, scientific research, and industrial applications. The kilogram dominates globally; the pound persists in the United States and the United Kingdom for everyday weights.

• ✓Adult body weight is measured in kilograms in most of the world and in pounds in the US. 70 kg equals about 154 lb — the ratio is roughly 1 : 2.2.
• ✓American recipes use ounces and cups; European recipes use grams. 1 oz ≈ 28.35 g.
• ✓Medicines are measured in milligrams (mg) or micrograms (µg). Never confuse the two — a factor of 1000 can be dangerous.
• ✓The metric ton (1000 kg), US short ton (907 kg) and UK long ton (1016 kg) are all different — always specify which "ton" in international trade.

• ✗Confusing a metric ton (1000 kg) with a US short ton (907 kg) in shipping contracts.
• ✗Using the regular ounce (28.35 g) when the recipe or the market calls for a troy ounce (31.10 g) for precious metals.
• ✗Weighing yourself at different times of day — body weight can vary 1–2 kg across a single day.
• ✗Confusing grams with milligrams on medication labels — the difference is 1000×.