physics

ISO/IEC 80000

ISO/IEC 80000 is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand ISO/IEC 80000 rather than just read about it. In short: ISO/IEC 80000, Quantities and units, is an international standard describing the International System of Quantities (ISQ). It was developed and promulgated jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC).

Key takeaways

ISO/IEC 80000 belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect ISO/IEC 80000 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of ISO/IEC 80000 from memory before moving on to harder problems.

Reference excerpt

ISO/IEC 80000, Quantities and units, is an international standard describing the International System of Quantities (ISQ). It was developed and promulgated jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). It serves as a style guide for using physical quantities and units of measurement, formulas involving them, and their corresponding units, in scientific and educational documents for worldwide use. The ISO/IEC 80000 family of standards was completed with the publication of the first edition of Part 1 in November 2009.

Overview By 2021, ISO/IEC 80000 comprised 13 parts, two of which (parts 6 and 13) were developed by IEC and the remaining 11 were developed by ISO, with a further three parts (15, 16 and, 17) under development. Part 14 was withdrawn.

Subject areas By 2021 the 80000 standard had 13 published parts. A description of each part is available online, with the complete parts for sale.

Part 1: General ISO 80000-1:2022 revised ISO 80000-1:2009, which replaced ISO 31-0:1992 and ISO 1000:1992. This document gives general information and definitions concerning quantities, systems of quantities, units, quantity and unit symbols, and coherent unit systems, especially the International System of Quantities (ISQ). The descriptive text of this part is available online. According to the standard, symbols for quantities are "generally single letters from the Latin or Greek alphabet" and are "written in italic (sloping) type". Examples include

density of heat flow rate: q = Φ / A electric current density: J = I / A magnetic flux density: B = Φ / A

Part 2: Mathematics ISO 80000-2:2019 revised ISO 80000-2:2009, which superseded ISO 31-11. It specifies mathematical symbols, explains their meanings, and gives verbal equivalents and applications. The descriptive text of this part is available online.

Part 3: Space and time ISO 80000-3:2019 revised ISO 80000-3:2006, which supersedes ISO 31-1 and ISO 31-2. It gives names, symbols, definitions and units for quantities of space and time. The descriptive text of this part is available online. A definition of the decibel, included in the original 2006 publication, was omitted in the 2019 revision, leaving ISO/IEC 80000 without a definition of this unit; a new part of the standard, IEC 80000-15 (Logarithmic and related quantities), is under development.

Part 4: Mechanics ISO 80000-4:2019 revised ISO 80000-4:2006, which superseded ISO 31-3. It gives names, symbols, definitions and units for quantities of mechanics. The descriptive text of this part is available online.

Part 5: Thermodynamics ISO 80000-5:2019 revised ISO 80000-5:2007, which superseded ISO 31-4. It gives names, symbols, definitions and units for quantities of thermodynamics. The descriptive text of this part is available online.

Part 6: Electromagnetism IEC 80000-6:2022 revised IEC 80000-6:2008, which superseded ISO 31-5 as well as IEC 60027-1. It gives names, symbols, and definitions for quantities and units of electromagnetism. The descriptive text of this part is available online.

Part 7: Light and radiation ISO 80000-7:2019 revised ISO 80000-7:2008, which superseded ISO 31-6. It gives names, symbols, definitions and units for quantities used for light and optical radiation in the wavelength range of approximately 1 nm to 1 mm. The descriptive text of this part is available online.

Part 8: Acoustics ISO 80000-8:2020 revised ISO 80000-8:2007, which revised ISO 31-7:1992. It gives names, symbols, definitions, and units for quantities of acoustics. The descriptive text of this part is available online. It has a foreword, scope introduction, scope, normative references (of which there are none), as well as terms, and definitions. It includes definitions of sound pressure, sound power, and sound exposure, and their corresponding levels: sound pressure level, sound power level, and sound exposure level. It includes definitions of the following quantities:

logarithmic frequency range static pressure sound pressure sound particle displacement sound particle velocity sound particle acceleration volume flow rate, volume velocity sound energy density sound energy sound power sound intensity sound exposure characteristic impedance for longitudinal waves acoustic impedance sound pressure level sound power level sound exposure level reverberation time

Part 13: Information science and technology

IEC 80000-13:2025 revised IEC 80000-13:2008, which replaced subclauses 3.8 and 3.9 of IEC 60027-2:2005 and IEC 60027-3. It defines quantities and units used in information science and information technology, and specifies names and symbols for these quantities and units. It has a scope; normative references; names, definitions, and symbols; and prefixes for binary multiples. Quantities defined in this standard are:

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with ISO/IEC 80000

Start with the simplest possible case. Write down what ISO/IEC 80000 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to ISO/IEC 80000 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about ISO/IEC 80000 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of ISO/IEC 80000

In research: ISO/IEC 80000 appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses ISO/IEC 80000 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: ISO/IEC 80000 is common in secondary-school and first-year university syllabi. It links to neighbouring topics ISO/IEC 80000, ISO/IEC standards, Measurement, so understanding it makes those chapters shorter.
In everyday life: Look for ISO/IEC 80000 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study ISO/IEC 80000 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what ISO/IEC 80000 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain ISO/IEC 80000 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is ISO/IEC 80000 in simple terms?

Why does ISO/IEC 80000 matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study ISO/IEC 80000?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on ISO/IEC 80000.