Unit Systems Around the World in 2026

The metric system is officially universal. In practice, most countries use a hybrid of metric and customary units, and the exact mix varies from place to place. Here is what a traveler, engineer, or curious observer needs to know.

Published 15 January 2026 · 10 min read

The Official Picture

Every country in the world has officially adopted the metric system except three: the United States, Liberia, and Myanmar. Even those three have nominal commitments to metrication, and their scientific, medical, and international trade sectors operate almost entirely in metric.

But official adoption does not mean everyday use. In many countries, customary units persist in specific contexts even where metric is the law.

The Fully Metric Countries

These countries use metric units almost exclusively in everyday life:

  • France, Germany, Italy, Spain, Netherlands, Belgium and most of continental Europe.
  • Australia, New Zealand.
  • Japan, South Korea, China, Taiwan.
  • Brazil, Argentina, Chile, Mexico and most of Latin America.
  • South Africa, Egypt, Kenya and most of Africa.
  • India, Pakistan, Bangladesh, Sri Lanka.
  • Russia and most of the former Soviet Union.

In these countries, weather is reported in Celsius, road distances in kilometers, body weight in kilograms, and food quantities in grams. Some exceptions exist (see below) but the metric system dominates.

The United States

The US remains the most visible outlier. Customary units dominate public life:

  • Road distances: miles, feet, yards.
  • Speeds: miles per hour.
  • Body weight: pounds.
  • Cooking: cups, ounces, tablespoons, Fahrenheit.
  • Weather: Fahrenheit.
  • Liquid volume (consumer): gallons, fluid ounces.
  • Construction: inches, feet, board feet.
  • Aviation: feet for altitude, nautical miles for distance, knots for speed.

Metric is used in science, medicine, engineering, military, and much of manufacturing. American students learn both systems, and technical professionals are fluent in metric. But everyday life remains customary, and there is no realistic prospect of full conversion in the near future.

The United Kingdom

The UK is a fascinating hybrid. Metric was officially adopted for most commerce and industry in the 1960s–70s, but some customary units persist:

  • Road distances: miles (road signs are required to be in miles).
  • Speeds: miles per hour.
  • Beer and cider: pints (imperial).
  • Body weight: stones (informal, especially among older generations).
  • Personal height: often in feet and inches.
  • Cooking: mixed — many recipes use metric, but older ones use imperial cups and ounces.

Everything else is metric: weather in Celsius, fuel in liters, groceries in grams, medical dosing in milligrams.

Canada

Canada is officially metric but has its own hybrid:

  • Road distances: kilometers (officially).
  • Speeds: km/h.
  • Weather: Celsius.
  • Body weight: pounds for many (especially older generations).
  • Real estate: square feet.
  • Cooking: mixed, with cups and Fahrenheit in older recipes.
  • Oven temperatures: Fahrenheit in older recipes; Celsius in newer ones.
  • Height of people: feet and inches in common speech.

Aviation: A Worldwide Exception

Global aviation uses a mix of customary and metric units, even in fully metric countries:

  • Altitude: feet worldwide.
  • Horizontal distance: nautical miles.
  • Speed: knots.
  • Vertical speed: feet per minute.
  • Runway length: meters or feet depending on the airport.
  • Wind speed: knots.
  • Temperature: Celsius (the one consistently metric measurement).

This exception is deeply embedded in international aviation standards (ICAO). Changing it would require retraining every pilot and re-equipping every aircraft, which is why it persists.

Maritime: Another Global Exception

Like aviation, international shipping uses knots for speed and nautical miles for distance. Weather reports at sea are in nautical miles and knots. Water depths are usually measured in meters, though feet are used in some US contexts.

Other Notable Exceptions

  • Screen sizes: TV, monitor, and phone screen diagonals are measured in inches worldwide, even in metric countries. A "55-inch TV" is sold in France, Japan, and Brazil with the same description.
  • Tire sizes: Tire dimensions are in inches worldwide (with metric width measurements in some cases). A "205/55R16" tire is understood everywhere.
  • Photography: Camera sensor sizes are specified in inches (or fractions of inches). A "1-inch sensor" is a standard category.
  • Sports: Track events are in meters; golf distances in yards (US) or meters (international); American football in yards; soccer in meters.
  • Computer components: RAM in binary GiB, drive capacity in decimal SI, screens in inches. The digital world has its own unit conventions.

Why Hybrid Systems Persist

Complete conversion to a single system has proven difficult because:

  1. The cost of changing is high. Road signs, school textbooks, manufacturing equipment, and consumer products all have to be redesigned.
  2. Consumers are comfortable. People know what a "pound of butter" feels like; switching to grams requires relearning.
  3. Industry standards are entrenched. A US-based industry that supplies customers worldwide cannot unilaterally change its units without disrupting its market.
  4. The systems can coexist. The US has been officially metric for over 150 years and functioning fine with a hybrid approach.
  5. Resistance is cultural, not technical. The technical work of conversion is trivial; the political and social work is not.

What This Means for Travelers and Professionals

  • Learn the rough conversions. 1 km ≈ 0.62 mi, 1 kg ≈ 2.2 lb, 1 m ≈ 3.3 ft, 1 L ≈ 1 qt, 20 °C ≈ 68 °F.
  • Check the country's conventions. A recipe from the UK may use imperial cups and metric grams in the same document.
  • Verify units in technical documentation. Aviation, shipping, and international standards have specific conventions that may not match the country's everyday habits.
  • Use tools that display units. A good converter shows the unit alongside the number, so you can verify what you are looking at.
  • Expect hybrid situations. The world is not divided into metric countries and customary countries — most countries are hybrids, just in different proportions.

The Future

Global metrication has slowed in recent decades. The remaining exceptions (US, and a few specific contexts like aviation and screens) appear stable. Whether they will eventually convert is uncertain, but there is no clear timetable.

What is certain is that the world will continue to use multiple unit systems for the foreseeable future, and the ability to convert between them accurately will remain a useful skill.