Conversions
Why the World Uses Metric (Except Three Countries)
Morecalcs Team 2026-08-03· 6 min
A short history of the meter, the yard, and the SI system.
The meter's origin
Defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. Redefined in 1983 as the distance light travels in 1/299,792,458 of a second — because light speed is the most reproducible ruler nature offers.
The three holdouts
The US, Liberia, and Myanmar are the only countries that haven't officially adopted metric. The US actually defines the inch as exactly 25.4 mm — metric under the hood.
Why metric won
Base-10 arithmetic, coherent unit relationships (1 L water = 1 kg), and no memorization of arbitrary conversion factors.
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