ISO 80000-4:2006

Overview

ISO 80000-4:2006, "Quantities and units - Part 4: Mechanics" (IEC/ISO collaboration), defines the names, symbols and definitions for quantities and units of classical mechanics. The standard organizes coherent SI units first, lists accepted non‑SI units for use with the SI, and provides conversion factors where appropriate. It replaces the earlier ISO 31-3 and aligns with the ISO 80000 series and SI/BIPM conventions.

Key topics

• Scope and purpose: Standardizes mechanical quantities to ensure consistent use of units and symbols across engineering, metrology and scientific documentation.
• Canonical quantities: Mass (m), mass density (ρ), momentum (p), force (F), weight (Fg), impulse (I), moment of inertia, angular momentum (L), moment/torque (M), gravitational constant (G), etc.
• Units and conversions:
  • Prescribes coherent SI units (kg, m, s, N, N·m, kg/m3, …).
  • Lists non‑SI units accepted for use with the SI and gives conversion factors (e.g., tonne = 1000 kg).
  • Includes informative annexes for CGS and foot–pound–second based units and other non‑SI units (Annex A, B, C).
• Notation and numerical statements:
  • Rules for exact (=), approximate (≈) and definitional (:=) equalities.
  • Guidance on expressing measurement uncertainty (e.g., 2.34782(32) m).
• Dimensionless quantities: Clarifies status of plane angle (rad) and solid angle (sr) as dimensionless derived units and when unit symbols may be used.
• Organization: Tabular presentation pairs quantity names, symbols and definitions (left pages) with units and conversion factors (right pages).

Applications and who uses it

ISO 80000-4 is essential for:

• Mechanical, aerospace, civil and automotive engineers standardizing design calculations, drawings and specifications.
• Metrologists and calibration labs ensuring consistent unit traceability and conversion.
• Standards bodies and technical committees harmonizing multi‑discipline documents.
• Software developers and data engineers implementing unit libraries, simulation tools and data exchange formats.
• Educators and researchers producing textbooks, papers and experimental reports with unambiguous quantities and uncertainties. Practical uses include technical documentation, instrument specifications, international project collaboration, regulatory compliance, and unit-aware scientific computing.

Related standards

• ISO 80000 series (Parts 1, 2, 3, 5, …) - general principles, math symbols, space & time, thermodynamics
• IEC 80000 Parts (e.g., Part 6 Electromagnetism)
• SI Brochure (BIPM) - for SI unit definitions and prefixes

Keywords: ISO 80000-4, quantities and units, mechanics, SI units, conversion factors, force, mass, torque, momentum, standards, unit of measurement.