Convert ounces to kilograms

One ounce is 0.0283495231 kilograms. To convert any amount, multiply by 0.0283495231. Going the other way, one kilogram is 35.2739619 ounces.

Multiply the ounce figure by 0.0283495231. So kg = oz × 0.0283495231. For a quick mental estimate, dividing by about 35.27 gets you close enough for most everyday purposes.

One ounce is about the mass of a slice of bread. The avoirdupois ounce is one sixteenth of a pound. It is distinct from the fluid ounce, which measures volume, and from the troy ounce used for precious metals.

One kilogram is a litre of water, near enough. The kilogram was redefined in 2019 in terms of the Planck constant, retiring the platinum-iridium cylinder in Paris that had defined it since 1889.

No, and the difference matters. The avoirdupois ounce here measures mass — one sixteenth of a pound, about 28.35 grams. A fluid ounce measures volume, about 29.6 mL in the US. They only coincide for water by rough accident, so substituting one for the other in a recipe will be wrong for anything denser or lighter. There is also the troy ounce, about 31.1 grams, used for precious metals.

Yes. Since the 1959 international yard and pound agreement, the imperial and metric systems are related by exact definitions rather than measurements — the inch is exactly 25.4 mm and the pound exactly 0.45359237 kg. Everything derived from those, including this conversion, is therefore exact. Round at the end rather than partway through, since rounding oz before converting introduces an error the conversion then multiplies.