Convert between common units of weight and mass including kilograms, pounds, ounces, grams, and more. Get instant conversions with precision and accuracy.
Weight and mass units have evolved throughout history from practical needs and scientific developments. While mass is a fundamental property of matter, weight varies based on gravitational force. Our calculator provides conversions between the most common weight and mass units used worldwide.
The metric system offers a logical, decimal-based approach to weight measurement, while imperial systems preserve historical traditions. Understanding these different systems helps in international communication, scientific work, and everyday applications.
| Unit | Equivalent in kg | Common Usage |
|---|---|---|
| kilogram [kg] | 1 kg (SI base unit) | Scientific measurements, body weight (metric) |
| pound [lb] | 0.453592 kg | Body weight (US/UK), everyday objects |
| gram [g] | 0.001 kg | Small objects, food ingredients, jewelry |
| ounce [oz] | 0.0283495 kg | Food portions, postal weights, precious metals |
| metric ton [t] | 1000 kg | Large objects, industrial materials, vehicles |
| stone [UK] | 6.35029 kg | Body weight in UK and Ireland |
| carat [ct] | 0.0002 kg | Gemstones, precious stones, diamonds |
| grain [gr] | 0.0000648 kg | Ammunition, pharmaceuticals, archery |
Early Babylonian and Egyptian records, as well as the Bible, indicate that weight was originally measured by the capacities of containers such as gourds or clay or metal vessels. These were filled with plant seeds that were then counted to measure the volumes. With the development of scales as a means of weighing, seeds and stones served as standards. For instance, the "carat," still used as a mass unit for gems, is derived from the carob seed.
The Babylonians invented the talent, as the basic unit of weight, and, based on their sexagesimal (60-based) system, divided it into equal parts in terms of that number. It was equal to the amount of water that filled an amphora (a kind of vase). The Greeks used the same weight measurement as the Babylonians, but the Romans changed it.
The metric system was developed by scientists in 18th century France. In 1791, the French parliament imposed the use of the metric system on the country, and it is now used in Continental Europe and many other parts of the world. The kilogram is defined as the mass of one liter of water under specific conditions.
The British Imperial System of Weights and Measures, also used in the U.S., has its roots in ancient Roman and Arab measurement systems. This system of units was first defined in the British Weights and Measures Act of 1824. The system came into official use across the British Empire and continues to be used in some countries today.
| Object | Weight/Mass |
|---|---|
| Milky Way Galaxy | 1.15357 × 10⁴² kg |
| Sun | 1.9891 × 10³⁰ kg |
| Earth | 5.9736 × 10²⁴ kg |
| Moon | 7.3477 × 10²² kg |
| Atomic Mass Unit | 1.660 × 10⁻²⁷ kg |
| Proton | 1.672 × 10⁻²⁷ kg |
| Electron | 9.109 × 10⁻³¹ kg |
Weight conversions are essential in international trade, cooking, fitness tracking, scientific research, and travel. Understanding different measurement systems helps in reading product labels, following recipes from different countries, tracking health metrics, and conducting business across borders.
In cooking, precise weight measurements often produce better results than volume measurements. In science and engineering, accurate weight conversions are crucial for calculations, specifications, and safety standards. Sports and fitness applications frequently require conversions between metric and imperial systems for training and competition purposes.