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Metric vs Imperial: The History and Future of Two Measurement Systems

The world is divided between two major measurement systems: the metric system (SI) used by virtually every country, and the imperial/US customary system used primarily in the United States, Liberia, and Myanmar. How did this division come about?

The Metric System: Born from Revolution

Conceived during the French Revolution (1790s), the metric system was designed as a rational, universal system. The meter was defined as one ten-millionth of the distance from the equator to the North Pole along a meridian. Key milestones: 1799 (platinum meter/kg standards created), 1875 (Treaty of the Meter established BIPM), 1960 (SI formally established), 2019 (SI redefined using fundamental physical constants).

Why it succeeded: Decimal base (powers of 10), coherence between units (1 mL water = 1 g), and international adoption by 195 countries.

The Imperial System: Tradition and History

Evolved from Roman, Anglo-Saxon, and Norman measurements over centuries:

  • **Inch**: Based on thumb width or three barleycorns
  • **Foot**: Based on human foot length
  • **Yard**: Henry I decreed it as nose-to-thumb distance
  • **Mile**: From Roman mille passus (1,000 paces)

    • The British Imperial system was standardized in 1824. US customary units diverged after American independence.

    Comparison

    Why the US Still Uses Imperial

  • **Colonial heritage**: Inherited British units at independence
  • **Cost of conversion**: Changing road signs, packaging, engineering standards would cost billions
  • **Cultural identity**: Many Americans view imperial as part of their identity
  • **Metric is already used**: Science (SI), military (NATO), soda (2L), medicine (metric), car engines (liters)

    • The Future

    Imperial persists in everyday US conversation but metric continues gaining ground globally. Being bilingual in both systems is the most practical approach.

    Use our Metric to Imperial Converter to convert between systems.

    Aspect Metric Imperial
    Countries using it 195 3 (US, Liberia, Myanmar)
    Year established 1795 (France) 1824 (British)
    Basis Decimal (Γ—10) Historical standards
    Subdivisions milli-, centi-, kilo- 12 in/ft, 3 ft/yd
    Scientific use Universal Minimal

    Try the Converter

    Metric to Imperial