What is a Weight Unit Converter?
The weight unit converter switches between kilograms, grams, pounds, and ounces.
How it's calculated
1 kg = 2.20462 lb, 1 lb = 453.592 g, 1 oz = 28.3495 g
Why precious metals use a different "ounce" worldwide
Gold, silver, and other precious metals are traded almost exclusively using the troy ounce (31.1g), a separate unit from the everyday avoirdupois ounce (28.35g) used for food and general goods. The troy system dates back to medieval European trade fairs and became the standard for weighing precious metals because it offered a consistent, widely-recognized reference across international markets long before modern metric standardization. Today, when financial news quotes "gold at $2,000 an ounce," that's always the troy ounce — mixing it up with the everyday ounce leads to a nearly 10% error.
Units that are easy to mix up
| Units | Why it's confusing | How to tell them apart |
|---|---|---|
| oz vs troy oz | Same name, different weight | Everyday oz = 28.35g, precious metals troy oz = 31.1g |
| kg vs kgf | Weight often used loosely for mass | kg is mass; kgf is a unit of force (weight) — different quantities |
| lb vs lbf | Same confusion as kg/kgf | lb is mass; lbf is force, common in US engineering specs |
There are actually two kinds of ounce
The everyday avoirdupois ounce (28.35g) used for food and general weight is different from the troy ounce (31.1g) used specifically for precious metals like gold and silver. So when international gold prices are quoted 'per ounce,' that's always the troy ounce — a common point of confusion.
Good to know
- The pound symbol 'lb' comes from the Latin libra (a balance scale) — the same root behind the zodiac sign Libra, and behind the British currency symbol £, which originally represented a pound's worth of silver.
- The kilogram is the only SI base unit with a prefix built into its name — an odd historical quirk, since 'gram' would seem like the more natural base unit.
- Until 2019, the kilogram was defined by an actual physical platinum-iridium cylinder kept in France. It's now defined using the Planck constant instead — a purely physics-based definition.
- For a quick estimate converting pounds to kilograms: divide by 2, then subtract 10%. 150 lb → 75 − 7.5 = 67.5 kg (actual: 68 kg).
- Gold, silver, and other precious metals are traded almost exclusively using troy ounces, distinct from the everyday ounce used for food packaging.
Frequently asked questions
Q. How many grams is 1 ounce?
28.35 g for the standard (avoirdupois) ounce used for everyday goods.
Q. What is a troy ounce?
A separate unit (31.1g) used specifically for precious metals like gold and silver — heavier than the everyday ounce.
Q. How do I quickly convert pounds to kg?
Divide by 2, then subtract about 10% for a close estimate.