Weight Converter

How to Use This Tool

The Professional Weight Converter makes it easy to switch between pounds, kilograms, ounces, grams, stones, and more. Enter any positive number in the input field, then pick your starting unit from the dropdown. Use the quick select buttons for common values like one kilogram or one pound. You can also adjust the precision to control how many decimal places you see.

All conversions appear in real time as you type. You can see how one unit compares to others instantly. The tool includes specialized units like troy ounces for precious metals and carats for gemstones. To make results easier to grasp, the tool adds real-world examples that show what each weight feels like in daily life. Copy any result directly to your clipboard for quick sharing or calculations.

Weight Conversion Facts

1. A gram is the base unit of mass in the metric system. Originally defined as the mass of one cubic centimeter of water at 4°C, it's now defined using the kilogram and fundamental physical constants. The word comes from the Greek “gramma” meaning small weight.
2. A kilogram equals 1,000 grams and is the fundamental SI unit of mass. It was originally defined as the mass of one liter of water at freezing point, but is now defined by fundamental physical constants including Planck's constant.
3. A pound equals exactly 453.592 grams. The word comes from the Latin libra pondo, meaning “pound weight,” which is why the symbol is “lb.” The avoirdupois pound is the most common pound used today.
4. An ounce (avoirdupois) equals exactly 28.3495 grams and is 1/16 of a pound. There are different types of ounces - avoirdupois (for general use), troy (for precious metals), and fluid ounces (for volume).
5. A stone equals exactly 14 pounds (6.35 kg) and is commonly used in the UK and Ireland for measuring body weight. It dates back to ancient times when people used actual stones as weight standards, though the official stone was standardized in 1835.
6. A tonne (metric ton) equals exactly 1,000 kilograms or 1,000,000 grams. It's different from the imperial ton (1016 kg in the UK, called a “long ton”) and the US ton (907 kg, called a “short ton”).
7. A troy ounce equals 31.1035 grams, making it about 10% heavier than a regular (avoirdupois) ounce. It's used exclusively for precious metals like gold, silver, and platinum. The name comes from the French city of Troyes, a major trading center in medieval times.
8. A carat equals exactly 200 milligrams (0.2 grams) and is used to measure gemstones and pearls. The name comes from carob seeds, which ancient merchants used as standard weights because of their uniform size and weight.
9. A grain is one of the oldest units of measurement, equal to 64.79891 milligrams. It was originally based on the weight of a single grain of barley. It's still used in some contexts, particularly for measuring bullets, arrows, and pharmaceutical compounds.
10. The long ton (UK) equals 1,016.047 kg (2,240 pounds) and was historically used in British commerce. It's 12% heavier than the US short ton and should not be confused with the metric tonne.

What Is The Difference between Weight and Mass?

Technically, weight measures the force of gravity on an object, while mass measures the amount of matter. On Earth, we often use these terms interchangeably, but an object's mass stays constant while its weight changes on different planets. In everyday terms, weight is what you measure on a scale, while mass is a measure of how much stuff is in an object.

Precision in Measurements

For everyday use, standard scales are accurate to the nearest gram or ounce. For scientific work, analytical balances can measure to 0.1 milligrams. For precious metals trading, measurements often go to three decimal places.

The kilogram is maintained by the International Bureau of Weights and Measures in France. Until 2019, it was defined by a physical platinum-iridium cylinder, but it's now defined using quantum mechanical constants.

Cultural Differences

While most of the world uses metric units (grams and kilograms), the United States primarily uses imperial units (ounces and pounds) for everyday measurements. The UK uses a mix of both systems.

Specialized Applications

Different industries prefer different units - jewelers use carats for gemstones, pharmacists use grains for medications, metallurgists use troy ounces for precious metals, and shipping companies use tonnes for cargo.