Unit Systems Guide
Every measurement relies on a unit system. Explore how the modern metric system (SI) is built on physical constants, and compare it with the imperial system and Japan’s traditional units.
International System of Units (SI)
The seven base units and the 2019 redefinition based on fixed physical constants.
SI Prefixes
From quetta (10³⁰) to quecto (10⁻³⁰): the 24 decimal multipliers.
Imperial & US Customary
Inches, feet, pounds and gallons — plus the UK vs US differences.
Shakkanho (Japanese Units)
Shaku, tsubo, go and koku: Japan’s traditional measures, still used today.
Museum of Unit Mistakes
From a lost Mars probe to the sinking of the Vasa — a museum of the disasters, costly blunders and funny stories caused by mixing up units.
Unit Origins & Stories
The name origins, birth stories and modern definitions of everyday units like the metre and kilogram.