how many countries have not adopted the metric or si system?
Only three countries have not fully adopted the metric system or SI units as
their primary system.
This longstanding fact highlights a rare holdout in global standardization,
where most nations embraced metric measurements decades ago for trade,
science, and daily life.
Key Holdouts
The United States, Liberia, and Myanmar remain the trio sticking primarily to customary or imperial units like inches, pounds, and gallons in everyday and official use.
- United States : Relies on US customary units due to historical ties to Britain, though metric is legal and used in science, medicine, and some industries—conversion efforts stalled since the 1970s.
- Liberia : Inherited imperial units from U.S. colonization but has partially adopted metric and plans full transition.
- Myanmar : Uses imperial-like units from British rule, with partial metric adoption underway amid modernization.
These countries represent less than 0.4% of the world's population, underscoring metric's dominance since its 1790s origins in France.
Partial Adopters and Trends
Many nations use metric officially but retain non-metric units for specific purposes—like the UK's pints for beer or Canada's mix in construction.
As of early 2026, no major shifts have occurred; Liberia and Myanmar continue gradual transitions, potentially leaving the U.S. alone soon.
Recent discussions on forums like Reddit note this as a quirky trivia point, with no 2025-2026 news of changes.
Why It Persists
Cultural inertia, economic costs, and education play roles—U.S. resistance stems from familiarity, despite metric's simplicity (base-10 vs. imperial's fractions).
Liberia and Myanmar face logistical hurdles from isolation or poverty.
Globally, 95%+ of countries are fully metric, aiding everything from Olympics to space missions.
TL;DR: Three countries (U.S., Liberia, Myanmar) haven't fully adopted metric/SI—stable as of 2026, with transitions in progress elsewhere.
Information gathered from public forums or data available on the internet and portrayed here.