Metric vs Imperial Guide
Learn the history, differences, and which countries use metric vs imperial systems
Overview
The world uses two main systems of measurement: the Metric System (also known as SI - International System of Units) and the Imperial System (also known as the British Imperial System). Understanding the differences between these systems is essential for science, commerce, travel, and everyday life.
While the metric system is used by the vast majority of countries worldwide, the imperial system remains in common use in the United States and a few other nations.
Historical Background
Origin: France, 1795
Created during the French Revolution to replace the chaotic collection of units used throughout Europe. Designed to be rational, universal, and based on natural phenomena.
The meter was originally defined as one ten-millionth of the distance from the equator to the North Pole.
Origin: Britain, 1824
Evolved from earlier English units that developed organically over centuries. Many units were based on human body parts or everyday objects.
The foot was literally based on the length of a human foot, and the inch on the width of a thumb.
Unit Comparison
| Measurement | Metric | Imperial | Conversion |
|---|---|---|---|
| Length | Meter (m) | Foot (ft) | 1 m = 3.281 ft |
| Mass/Weight | Kilogram (kg) | Pound (lb) | 1 kg = 2.205 lb |
| Volume | Liter (L) | Gallon (gal) | 1 L = 0.264 gal |
| Temperature | Celsius | Fahrenheit | F = C x 9/5 + 32 |
| Distance | Kilometer (km) | Mile (mi) | 1 km = 0.621 mi |
| Area | Square meter | Square foot | 1 m2 = 10.764 ft2 |
Which Countries Use Each System?
Used by virtually every country in the world, including:
- All of Europe
- China, Japan, South Korea
- Australia, New Zealand
- Canada (officially)
- All of South America
- All of Africa
Only three countries have not officially adopted metric:
- United States - Uses US Customary units
- Myanmar - Transitioning to metric
- Liberia - Transitioning to metric
Note: UK uses a mix of both systems
Advantages of Each System
Metric Advantages
- Decimal-based: Easy conversions (multiply/divide by 10)
- Universal: Used internationally in science and trade
- Consistent: Logical prefixes (kilo-, centi-, milli-)
- Interconnected: Units relate to each other (1L water = 1kg)
Imperial Advantages
- Human-scale: Foot, inch feel intuitive for daily use
- Divisibility: 12 inches divides evenly by 2, 3, 4, 6
- Familiarity: Deeply embedded in US culture
- Practical: Some argue better for construction
Quick Conversion Tips
Here are some easy-to-remember approximations for quick mental conversions:
1 inch = 2.5 cm
1 meter = 3 ft 3 in
1 mile = 1.6 km
1 kg = 2.2 pounds
1 ounce = 28 grams
1 pound = 450 grams
1 liter = 1 quart
1 gallon = 4 liters
1 cup = 240 ml
0C = 32F (freezing)
20C = 68F (room)
37C = 98.6F (body)