Metric vs Imperial — Why Two Systems Still Exist in 2026

Most of the world uses metric. The United States, Liberia and Myanmar don't. Here's why the imperial system has survived, and what it means for anyone working across borders.

The metric system was designed in France during the Revolution of the 1790s, with one goal: to replace the chaos of regional measurement systems with a single, rational, decimal-based standard. By almost every measure it succeeded — 195 of the world's 198 countries now use it as their official system of measurement.

The three holdouts — the United States, Liberia and Myanmar — are notable for very different reasons. Myanmar and Liberia have been making slow progress toward metrication for decades. The United States is a more complex case: the country officially adopted the metric system in 1975 with the Metric Conversion Act, but made conversion entirely voluntary, and voluntary conversion largely did not happen.

The result is a system where American scientists, doctors and the military use metric exclusively, American international trade is conducted largely in metric, and American consumer products are labelled in both — while everyday American life continues in miles, pounds and Fahrenheit.

For anyone converting between the two systems regularly, the key relationships to memorise are: 1 inch = 2.54 centimetres exactly, 1 mile = 1.60934 kilometres, 1 kilogram = 2.20462 pounds, and the Celsius-Fahrenheit formula °F = (°C × 9/5) + 32. Everything else can be derived from a converter.