Mole Day2026 · Date · History
The National Mole Day Foundation observes Mole Day on October 23 from 6:02 a.m. to 6:02 p.m., using the 6.02 × 10^23 notation for the Avogadro constant as the date-and-time mnemonic; its history traces the foundation to Maurice Oehler in 1991.
About Mole Day
Mole Day is a chemistry-education observance held on October 23, traditionally from 6:02 a.m. to 6:02 p.m.
Its date-and-time format is a mnemonic for the Avogadro constant, approximately 6.022 × 10²³ entities per mole.
Why Mole Day matters
The observance is designed to make the mole—a central unit for counting particles in chemistry—more approachable through classroom demonstrations, puzzles and themed activities.
Mole Day is an education campaign rather than a statutory holiday; schools and chemistry groups decide for themselves how to participate.
History of Mole Day
The National Mole Day Foundation traces the idea to an early-1980s article in The Science Teacher.
Chemistry teacher Maurice Oehler organized the National Mole Day Foundation in 1991, and professional science-education histories place the first Mole Day celebration on October 23, 1991.
The Foundation later incorporated as a nonprofit and continues to promote chemistry education around the annual observance.
How the observance developed
This timeline uses documented milestones from reviewed sources. Missing stages are left out rather than guessed.
Maurice Oehler / National Mole Day Foundation
The Foundation history credits chemistry teacher Maurice Oehler with creating the National Mole Day Foundation in 1991 after the observance idea circulated in science education.
National Mole Day Foundation
The Foundation is the organized body that established and promotes the annual chemistry-education observance.
First documented observance
Royal Society of Chemistry education material identifies 1991 as the first Mole Day celebration, consistent with Foundation history.
National Mole Day Foundation
The Foundation continues to publish and promote Mole Day materials.
What the evidence establishes
Confirmed institutional roles and milestones are shown first. Details that could not be established from the reviewed sources are listed separately below.
4 fields not established in reviewed sources
How to Observe Mole Day
Use 6.022 × 10²³ as a starting point for explaining what a mole represents in chemistry.
Run a safe classroom estimation, counting or stoichiometry activity tied to the mole concept.
Compare everyday counting units such as a dozen with the much larger chemical counting unit.
Keep demonstrations age-appropriate and follow normal laboratory-safety requirements.
Mole Day Facts
Mole Day is observed on October 23.
The traditional 6:02 a.m.–6:02 p.m. window mirrors the 6.02 part of the Avogadro-number mnemonic.
The National Mole Day Foundation was organized in 1991 by chemistry teacher Maurice Oehler.
Professional science-education material dates the first celebration to October 23, 1991.
Mole Day is an educational observance, not a government holiday.
Topic and context
What this page does not assume
- Keep the source-defined country, community, organizer or institutional scope; do not silently broaden it.
- Do not treat the title alone as proof of government recognition or public-holiday status.
- Do not add a creator, founding story or origin claim unless the supporting evidence establishes it.
Evidence & sources
Sources used across the guide are gathered here. Labels show how each source supports the page, and contextual references are kept separate from primary evidence.
National Mole Day Foundation — History of the Foundation (opens in a new tab)
Official Organizer History
National Mole Day Foundation — Mole Day (opens in a new tab)
Official Organizer
Royal Society of Chemistry Education — Mole Day (opens in a new tab)
Professional Science Education
University of Wisconsin–Madison Badger Chemist — Mole Day created by Badger chemist (opens in a new tab)
University History
Understand it, compare it, then explore further
Start with the most common factual questions, then compare closely related observances and explore useful connections.
Frequently asked questions
When is Mole Day?
23 October, traditionally 6:02 a.m. to 6:02 p.m. The documented recurrence rule is: 23 October, traditionally 6:02 a.m. to 6:02 p.m..
Does Mole Day fall on the same date every year?
Yes. It uses a fixed annual date unless stronger evidence changes the pattern.
Is Mole Day an official public holiday?
The reviewed sources verify it within this scope: International chemistry-education observance led by the National Mole Day Foundation. That recognition does not by itself make it a statutory public holiday; the site only makes public-holiday claims when reliable evidence explicitly does so.
Who established or recognizes Mole Day?
The reviewed sources identify National Mole Day Foundation as the proclaiming or establishing body. The proposer or originator is recorded separately as Maurice Oehler / National Mole Day Foundation. Current facilitation or coordination is recorded as National Mole Day Foundation.
Is Mole Day international or country-specific?
The documented scope is international or global: International chemistry-education observance led by the National Mole Day Foundation. That does not mean every country treats the date as a public holiday or observes it in the same way.
How is this page verified?
The factual information is checked against reviewed sources, including the date pattern, scope and institutional history. This page was checked on 2026-09-18.
When is Mole Day?
Mole Day is observed on October 23, traditionally from 6:02 a.m. to 6:02 p.m.
Why October 23 at 6:02?
The 6:02 and 10/23 notation forms a mnemonic for approximately 6.02 × 10²³, the number associated with the mole in chemistry.
Who started Mole Day?
The National Mole Day Foundation’s history credits chemistry teacher Maurice Oehler with creating the Foundation in 1991 after the idea had circulated in science-education writing.
Is Mole Day an official public holiday?
No. It is a chemistry-education observance promoted by the National Mole Day Foundation and participating educators.
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