Weight Converter

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.

The kilogram is the base SI unit of mass and the global standard for body weight, food, and commerce.

The gram is the everyday metric unit for cooking ingredients, postage, and small product weights worldwide.

The milligram is the standard unit for pharmaceutical dosing, vitamin labeling, and chemistry lab measurements.

The microgram is used in pharmacology, environmental science, and trace-element nutritional analysis.

The pound is the everyday weight unit in the United States and the United Kingdom, deeply rooted in commerce and daily life.

The ounce is the standard small-weight unit in American kitchens, postage, and precious-metal trading.

The metric ton equals 1,000 kilograms and is the international standard for shipping, agriculture, and industrial weight.

The US short ton equals 2,000 pounds and is the standard unit for American freight, mining, and construction.

The UK long ton equals 2,240 pounds and remains in British shipping, mining, and historical engineering contexts.

The stone equals 14 pounds and is the traditional British unit for personal body weight, still widely used today.

The carat equals 200 milligrams exactly and is the universal unit for gemstone and diamond weight in jewelry.

The grain is the smallest traditional weight unit, used in pharmaceutical compounding, ammunition, and arrow tips.

• ✓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×.