Convert Ounces to Kilograms

About converting Ounces to Kilograms

Ounces (oz) and Kilograms (kg) are both units of weight & mass, so converting between them is a single multiplication: multiply your Ounces figure by 0.02835. Ten Ounces comes to 0.2835 Kilograms, and a hundred works out at 2.835 Kilograms.

Rule of thumb: going from Ounces to Kilograms divides, so the figure always shrinks — it takes about 35.274 Ounces to make a single Kilogram. If your answer came out bigger, you have the conversion the wrong way round.

What is an Ounce?

The ounce here is the avoirdupois ounce, one sixteenth of a pound, and the qualifier matters. The troy ounce used to price gold and silver is noticeably heavier, so a "one ounce" gold coin is not an ounce of anything else — a confusion that has cost people real money. Muddier still is the fluid ounce, which measures volume rather than mass and differs between the US and the UK. The name comes from the Latin uncia, a twelfth part: it was a twelfth of the Roman libra, and the move to sixteen ounces to the pound came later.

What is a Kilogram?

The kilogram was the last SI unit still defined by a physical object — the International Prototype Kilogram, a platinum-iridium cylinder kept in a vault near Paris since 1889. The problem was that it drifted. Careful comparisons against its official copies showed the masses diverging by tens of micrograms, and because the prototype simply was the kilogram by definition, there was no way to say which side had changed. In 2019 it was redefined in terms of the Planck constant, so any properly equipped lab can now realise a kilogram from physics rather than from an artefact.

To put both in perspective: a slice of sandwich bread weighs about an ounce, while a liter of water weighs about a kilogram.

The converter above updates as you type, and the table lists common values for quick reference. Need the opposite direction? Use the Kilograms to Ounces converter, or browse all Weight & Mass converters.