Definition
The Endo is a proposed unit of length designed to provide an intuitive, human-centered approach to measurement. Unlike abstract scientific definitions, the Endo is anchored to a tangible, globally recognized object: the short edge of an A4 paper sheet.
This definition provides an immediately relatable physical reference. A4 paper is ubiquitous in offices, schools, and homes worldwide, making the Endo inherently more intuitive than abstract metric definitions. The choice of 21 centimeters represents a deliberate return to anthropocentric principles while maintaining the precision and scalability of modern metrology.
Unit System
The Endo system employs standard SI prefixes, ensuring compatibility with scientific notation and facilitating seamless conversion across scales. The following table presents the primary units used in everyday applications:
| Unit Name | Symbol | Endo Equivalent | Metric Equivalent |
|---|---|---|---|
| Kiloendo | k-endo | 1,000 endo | 210 m |
| Hectoendo | h-endo | 100 endo | 21 m |
| Decaendo | da-endo | 10 endo | 2.1 m |
| Endo | endo | 1 endo | 21 cm |
| Deciendo | d-endo | 0.1 endo | 2.1 cm |
| Centiendo | c-endo | 0.01 endo | 2.1 mm |
| Milliendo | m-endo | 0.001 endo | 0.21 mm |
Conversion Formula
Converting between Endo and metric units is straightforward:
- To Endo: Length (cm) ÷ 21 = Length (endo)えんどうへ：
- To Centimeters: Length (endo) × 21 = Length (cm)センチメートルへ：
Conversion Calculator
Use this tool to quickly convert between centimeters and Endo units.
Real-World Applications
The Endo system offers practical advantages across multiple domains. Below are common objects and their measurements in Endo units:
A4 Paper Sheet
Short edge of standard A4 paper
500ml Water Bottle
Typical height of common beverage bottle
Standard Doorway
Typical residential door height (90 cm)
Adult Stride
Average walking stride length (70 cm)
Laptop Screen
Typical 15-inch laptop diagonal (13-14 inches)
Human Arm Span
Average adult arm span (180 cm)
Research & Documentation
The Endo Research Group (AI) has published comprehensive documentation on the theoretical foundations, mathematical properties, and practical applications of the Endo unit system. Access our official whitepaper below:
The Endo: A Comprehensive Study of an Anthropocentric Unit of Length
Authored by The Endo Research Group (AI) | January 2026 | PDF Format
Whitepaper Contents
The official whitepaper provides an in-depth analysis including:
- Historical context of measurement systems and anthropocentric units
- Mathematical foundations and conversion formulas
- Comprehensive unit system with SI prefixes (Teraendo to Picoendo)
- Practical applications in design, architecture, and education
- Cognitive and societal benefits of intuitive measurement
- Future research directions and standardization efforts