Convert ounces to tonnes

One ounce is 0.0000283495231 tonnes. To convert any amount, multiply by 0.0000283495231. Going the other way, one tonne is 35273.9619 ounces.

Multiply the ounce figure by 0.0000283495231. So t = oz × 0.0000283495231. For a quick mental estimate, dividing by about 35273.96 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 tonne is a small car. The tonne — metric ton — is exactly 1,000 kilograms. It differs from the US short ton (907 kg) and the UK long ton (1,016 kg), which is a genuine source of freight errors.

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.