Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Physical Measurement Laboratory

Office of Weights and Measures

SI Units – Amount of Substance

Resources for Students and Teachers | League of SI Superheroes – The Mole

One mole (mol) contains exactly 6.02214076 × 10²³ elementary entities. This number is the fixed numerical value of the Avogadro constant, N_A, when expressed in the unit mol⁻¹ and is called the Avogadro number. The amount of substance, symbol n, of a system is a measure of the number of specified elementary entities. An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles.

When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.

The SI unit of concentration (of amount of substance) is the mole per cubic meter (mol/m³).

Resources for Students and Teachers

Teachers: Top 10 Tips for Teaching the Metric System. (NIST)

Not sure how to tell that scientific minded person in your life how you feel? Maybe our Superhero Valentine's Day cards will do the trick.
Download these fun coloring pages for Mole and our SI Superheroes.
The Metric Meal (option 2) focuses exclusively on length measurements and uses a multidisciplinary approach to build measurement skills.

League of SI Superheroes - Mole
- This comic book-style video animation series has been developed to help middle school students learn about the 7 SI base measurement units.
SI Units Card Deck (SP 1297) - this activity offers a fun way to enhance understanding of the International System of Units. (NIST)
Metric Estimation Game (SP 1336) - this fun, hands-on activity helps participants become familiar with SI measurements by practicing estimation skills. During this activity, participants will become familiar with using the metric system (International System of Units, SI) measurements on common, everyday items.

Metric Estimation Game (SP 1336) - this fun, hands-on activity helps participants become familiar with SI measurements by practicing estimation skills. During this activity, participants will become familiar with using the metric system (International System of Units, SI) measurements on common, everyday items.
SI Base Units Relationship Poster (SP 1247) (NIST) – a colorful poster illustrating the relationships of the International System of Units (SI) derived units with special names and symbols and the seven traditional base units.
SI Units Card Deck (SP 1297) (NIST) – this activity offers a fun way to enhance understanding of the International System of Units, including the defining constants, base units, derived units with special names, and prefixes.
National Mole Day – Celebrated annually on October 23 from 6:02 a.m. to 6:02 p.m. to commemorate Avogadro's Number (6.02 x 10²³). (National Mole Day Foundation)
Mole Day (American Chemical Society)
Introduction to the Mole (Pennsylvania Department of Education)- This lesson introduces students to the mole concept in chemistry.
How Big is a mole (TedEd)

Metric Estimation Game (SP 1336) - this fun, hands-on activity helps participants become familiar with SI measurements by practicing estimation skills. During this activity, participants will become familiar with using the metric system (International System of Units, SI) measurements on common, everyday items.
SI Base Units Relationship Poster (SP 1247) (NIST) – a colorful poster illustrating the relationships of the International System of Units (SI) derived units with special names and symbols and the seven traditional base units.
SI Units Card Deck (SP 1297) (NIST) – this activity offers a fun way to enhance understanding of the International System of Units, including the defining constants, base units, derived units with special names, and prefixes.
Redefining the Mole (NIST)- Scientists redefined the mole using a constant number of particles instead of a physical object, making chemical measurements more accurate and universal. 9
National Mole Day – Celebrated annually on October 23 from 6:02 a.m. to 6:02 p.m. to commemorate Avogadro's Number (6.02 x 10²³). (National Mole Day Foundation)
Mole Day (American Chemical Society)
Mole Day – Avogadro & the Mole (Compound Interest)- Mole Day celebrates the chemistry unit "mole," which is 6.022 × 10²³ particles. It helps scientists measure substances and predict chemical reaction outcomes. 9
The Mole – Practice mole calculations. (Jason Learning)
Introduction to the Mole (Pennsylvania Department of Education)- This lesson introduces students to the mole concept in chemistry.
Amedeo Avogadro (Science History Institute)
Introducing High School Students to the Avogadro Number and the Mole Concept Using Discovery with Calculations Based on Physical Properties of Elements, Crystal Structures, and 28Si Spheres, Journal of Chemical Education, 98, 3, 790-795. T. H. Bindel. (January 29, 2021) – DOI: 10.1021/acs.jchemed.0c01132. Explore an instructional approach where students discover the Avogadro number and the mole concept.

Return to Top of Page

League of SI Superheroes – The Mole

This comic book-style video animation series has been developed to help middle school students learn about the 7 SI base measurement units. Able to sniff out and count the atoms of every element, the Mole is the king of chemistry. Equal to about 600 sextillion (that's a 6 followed by 23 zeros!), a mole is a shorthand way to talk about huge numbers, especially of tiny things.