Metric vs imperial in Australia

Australia uses the metric system for everyday life: road distances in kilometres, speed limits in kilometres per hour, weather in degrees Celsius, body weight in kilograms, and groceries in grams, kilograms, millilitres, and litres. If you are reading a road sign, a weather forecast, or a supermarket label in Australia, expect metric first.

Where imperial still appears

Imperial units have not disappeared. They survive where a product, hobby, or import comes from a country that still uses them. Tyre and wheel sizes are commonly given in inches, television and monitor screens are sold by their diagonal in inches, and a person's height is often quoted in feet and inches in conversation even when it is measured in centimetres. Imported recipes and manuals can also use pounds, ounces, cups, and fluid ounces.

The practical rule

The practical rule is simple: convert at the boundary, and check the unit before you convert. A litre figure converted with the US gallon factor gives a different answer from the same figure converted with the imperial gallon factor, and a screen size in inches is a diagonal measurement, not a width. This converter states which gallon and which fluid ounce it uses on the home page, so the same input always gives the same answer.