Comparison guide
Metric vs Imperial Units
Metric and imperial units often measure the same thing but use different reference points and scaling rules. This guide summarizes the practical differences.
How metric works
Metric units are decimal. A kilometer is 1000 meters, a centimeter is one hundredth of a meter, and a milliliter is one thousandth of a liter. This makes mental conversion easier.
How imperial works
Imperial and US customary units use fixed relationships such as 12 inches in a foot, 3 feet in a yard, 5280 feet in a mile, and 16 ounces in a pound. These are familiar in countries that use them daily.
Where confusion happens
Volume units need special care because a US gallon and UK imperial gallon are not the same. Temperature also needs formulas rather than a simple multiplication factor.
Useful converters
Common cross-system conversions include cm to inches, meters to feet, kg to lbs, liters to gallons, mph to kph, and Celsius to Fahrenheit.