ISO 80000: Quantities and Units (13 Main Parts)

ISO/IEC 80000 organises measurement science into 13 coordinated parts. This companion article complements our narrative overview with at-a-glance tables that show the most cited quantities, symbols and coherent SI units from each part.

Use the summaries to connect documentation tasks with quick conversions. Each section ends with calculators or deep dives across CalcSimpler so you can validate real-world numbers immediately.

ISO 80000 overview International System of Units (SI) Measurement foundations

Part 1 — General

Introduces the International System of Quantities (ISQ), the SI base units and the angular quantities that underpin every other chapter.

Quantity	Symbol	Unit
Length	l	metre (m)
Mass	m	kilogram (kg)
Time	t	second (s)
Electric current	I	ampere (A)
Thermodynamic temperature	T	kelvin (K)
Amount of substance	n	mole (mol)
Luminous intensity	I_v	candela (cd)
Plane angle	θ	radian (rad)
Solid angle	Ω	steradian (sr)

ISO 80000 primer ISO 80000-1 general principles International System of Units guide

Part 2 — Mathematical signs and symbols

Collects the algebraic operators, calculus symbols and functional notation that the physical quantities rely on. No additional units are introduced here, but the typography rules ensure clarity in derived expressions.

This part focuses on notation conventions—keep it handy when typesetting equations or documenting conversions.

ISO 80000-2 mathematical signs and symbols Logarithm base conversion

Part 3 — Space and time

Extends the base quantities into geometric measures, frequency and kinematics for motion analysis.

Quantity	Symbol	Unit
Area	A	square metre (m²)
Volume	V	cubic metre (m³), litre (L)
Time interval	t	second (s), minute (min), hour (h)
Frequency	f, ν	hertz (Hz = 1/s)
Period	T	second (s)
Plane angle	θ, φ	radian (rad), degree (°)
Solid angle	Ω	steradian (sr)
Speed	v	metre per second (m/s), kilometre per hour (km/h)
Acceleration	a	metre per second squared (m/s²)

ISO 80000-3 space and time guide Meters to feet converter Kilometers to nautical miles What is a unit of measurement?

Part 4 — Mechanics

Defines force-centric quantities that describe motion, deformation and energy transfer.

Quantity	Symbol	Unit
Force	F	newton (N = kg·m/s²)
Momentum	p	newton second (N·s)
Pressure, stress	p	pascal (Pa = N/m²)
Work, energy	W, E	joule (J = N·m)
Power	P	watt (W = J/s)
Torque (moment of force)	M, τ	newton metre (N·m)
Density	ρ	kilogram per cubic metre (kg/m³)

ISO 80000-4 mechanics guide Torque Nm to ft-lb kWh to MJ Hydrostatic pressure

Part 5 — Thermodynamics

Captures the energetic view of heat, entropy and the material properties needed for energy balances.

Quantity	Symbol	Unit
Thermodynamic temperature	T	kelvin (K)
Celsius temperature	t	degree Celsius (°C)
Heat (thermal energy)	Q	joule (J)
Internal energy	U	joule (J)
Enthalpy	H	joule (J)
Entropy	S	joule per kelvin (J/K)
Heat capacity	C	joule per kelvin (J/K)
Specific heat capacity	c	J/(kg·K)
Pressure	p	pascal (Pa)

ISO 80000-5 thermodynamics guide Celsius to Kelvin Ideal gas pressure

Part 6 — Electromagnetism

Specifies the electrical and magnetic field quantities that show up in circuitry, power systems and field theory.

Quantity	Symbol	Unit
Electric current	I	ampere (A)
Electric charge	Q, q	coulomb (C = A·s)
Electric potential (voltage)	U, V	volt (V)
Resistance	R	ohm (Ω)
Capacitance	C	farad (F)
Inductance	L	henry (H)
Electric field strength	E	volt per metre (V/m)
Magnetic field strength	H	ampere per metre (A/m)
Magnetic flux	Φ	weber (Wb)
Magnetic flux density	B	tesla (T)

ISO 80000-6 electromagnetism guide Ohm's law voltage calculator Electronvolt to joule

Part 7 — Light and radiation

Aligns photometric and radiometric terms so lighting, imaging and sensor teams can communicate precisely.

Quantity	Symbol	Unit
Luminous intensity	I_v	candela (cd)
Luminous flux	Φ_v	lumen (lm = cd·sr)
Illuminance	E_v	lux (lx = lm/m²)
Luminance	L_v	candela per square metre (cd/m²)
Radiant flux	Φ_e	watt (W)
Radiant intensity	I_e	watt per steradian (W/sr)
Irradiance	E_e	watt per square metre (W/m²)
Wavelength	λ	metre (m), typically expressed in nanometres (nm)

ISO 80000-7 light and radiation guide Lux to lumens Lux to foot-candles

Part 8 — Acoustics

Standardises sound pressure, intensity and exposure quantities used in environmental and product noise studies.

Quantity	Symbol	Unit
Sound pressure	p	pascal (Pa)
Sound intensity	I	watt per square metre (W/m²)
Sound power	P	watt (W)
Sound pressure level	L_p	decibel (dB), reference 20 µPa
Frequency	f	hertz (Hz)
Speed of sound	c	metre per second (m/s)
Sound exposure	H	pascal squared second (Pa²·s)

ISO 80000-8 acoustics guide Decibel to power percentage

Part 9 — Physical chemistry and molecular physics

Applies the ISQ conventions to mixtures, reactions and molecular properties.

Quantity	Symbol	Unit
Amount of substance	n	mole (mol)
Concentration	c	mol/m³ (mol/L in chemistry)
Mole fraction	x, y	dimensionless
Molar mass	M	kilogram per mole (kg/mol)
Molar volume	V_m	cubic metre per mole (m³/mol)
Atomic mass unit	u	1 u ≈ 1.6605×10⁻²⁷ kg
Avogadro constant	N_A	6.022×10²³ mol⁻¹
Catalytic activity	z	katal (kat = mol/s)

ISO 80000-9 physical chemistry guide Ideal gas pressure pH from concentration

Part 10 — Atomic and nuclear physics

Establishes coherent activity, decay probability, cross-section and dosimetry units so nuclear labs, safeguards teams and healthcare providers speak the same measurement language.

Quantity	Symbol	Unit
Activity	A	becquerel (Bq = s⁻¹)
Decay constant	λ	per second (s⁻¹)
Half-life	T_1/2	second (s)
Neutron flux	Φ	per square metre per second (m⁻²·s⁻¹)
Microscopic cross-section	σ	square metre (m²), barn (1 b = 10⁻²⁸ m²)
Absorbed dose	D	gray (Gy = J/kg)
Dose equivalent	H	sievert (Sv)

ISO 80000-10 atomic and nuclear physics guide Radioactive decay remaining Electronvolt to joule

Part 11 — Characteristic numbers

Lists dimensionless ratios like Reynolds, Mach and Prandtl numbers that compare forces or transport mechanisms.

Number	Symbol	Definition / Focus
Reynolds number	Re	Inertial vs viscous forces
Mach number	Ma	Object speed / speed of sound
Prandtl number	Pr	Momentum diffusivity / thermal diffusivity
Nusselt number	Nu	Convective vs conductive heat transfer
Froude number	Fr	Inertia vs gravitational forces
Coefficient of friction	μ	Friction force / normal force

ISO 80000-11 characteristic numbers guide Reynolds number calculator

Part 12 — Solid state physics

Covers material properties such as elasticity, conductivity and thermal transport.

Quantity	Symbol	Unit
Density	ρ	kilogram per cubic metre (kg/m³)
Specific heat capacity	c	joule per kilogram kelvin (J/(kg·K))
Thermal conductivity	λ, k	watt per metre kelvin (W/(m·K))
Young's modulus	E	pascal (Pa)
Poisson's ratio	ν	dimensionless
Electrical resistivity	ρ	ohm metre (Ω·m)
Electrical conductivity	σ	siemens per metre (S/m)
Permittivity	ε	farad per metre (F/m)
Permeability	μ	henry per metre (H/m)

ISO 80000-12 solid state physics guide Specific Heat Energy Calculator R-Value to U-Value Converter

Part 13 — Information science and technology

Anchors information theory, computing and telecom measurements with coherent units and binary prefixes.

Quantity	Symbol	Unit
Information content	I	bit (b), byte (B = 8 b)
Storage capacity	—	bit or byte (kB, MB, GB, etc.)
Data transfer rate	r	bit per second (bit/s), byte/s
Traffic intensity	A	erlang (E)
Information entropy	H	shannon (Sh), nat, hartley
Information rate	R	bit per second (bit/s)
Clock frequency	f_cl	hertz (Hz)
Modulation rate	r_m	baud (Bd = symbols/s)

ISO 80000-13 information science guide Bandwidth-delay product Live streaming bandwidth