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National Mole Day

Celebrate National Mole Day with us and explore the world of chemistry! Join in on activities, experiments, and fun learning opportunities.

Friday

October 2026

Last updated February 7, 2026 · by the Holiday Calendar Team

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YEARLY DATEOctober 23

OBSERVED INUnited States

CATEGORYSchool

SUBCATEGORYSTEM

INTRO

Introduction

PHOTO

It's time to party on National Mole Day, which falls on October 23! This day has been around since 1991 and celebrates Avogadro's Number (6.02x10^23), a fundamental measurement in chemistry. Celebrate by having a mole-themed party with your friends or family, complete with mole-shaped cookies and drinks! Whether you're an experienced chemist or someone who is just getting started in the field, National Mole Day is the perfect opportunity for everyone to get together and have some fun while learning about this important part of science.

TIMELINE

National Mole Day Timeline

Avogadro's Hypothesis

Italian scientist Amedeo Avogadro introduces his hypothesis that equal volumes of gases, at same temperature and pressure, contain an equal number of molecules.

Avogadro's Number Defined

Johann Josef Loschmidt first estimates the size of a molecule, leading to the calculation of Avogadro's number.

Development of Mole Concept

Chemist Wilhelm Ostwald proposes the term "mole" as a unit of measurement in chemistry to represent Avogadro's number.

Mole Standardization

The International Committee for Weights and Measures standardizes the mole as a base unit in the International System of Units (SI).

First National Mole Day

National Mole Day is first celebrated by Maurice Oehler, a high school chemistry teacher in Prairie du Chien, Wisconsin.

GET INVOLVED

How to Celebrate National Mole Day

Organize a mole scavenger hunt

Create a list of items or clues that your students must find related to moles and chemistry. This is a great way to get your students excited about moles and chemistry.

WATCH

Watch a mole-themed movie

Find a chemistry-related movie to watch with your students. There are many movies and documentaries that explore the fascinating world of moles and their role in chemistry.

DESIGN

Design a mole costume

Have your students design their own mole costume, complete with elements from the periodic table. Have a contest for the most creative design.

MAKE

Make mole cookies

Making mole cookies is a fun and creative way to celebrate National Mole Day. Use cookie cutters shaped like moles or draw them out on paper and cut them out with scissors.

CREATE

Create a mole art project

Have your students create a project using moles as the theme. This could be in the form of a painting, sculpture, collage, or any other type of art project.

WHY THIS DAY MATTERS

Why We Love National Mole Day

It encourages problem solving

Mole Day provides an excellent opportunity for students to practice their problem solving skills. By practicing with mole calculations, students are able to build their confidence while becoming stronger at math and science. At the same time, it's an enjoyable way for them to engage with chemical concepts in a meaningful way!

Mole Day celebrates chemistry

Mole Day is a national holiday that pays tribute to chemistry and the mole concept. It's an opportunity for chemists of all ages to appreciate the importance of atomic mass and molarity formulas in science.

It brings scientific awareness

The holiday is also used as a way to encourage more people to learn about and appreciate chemistry by providing educational activities, experiments, lectures, and contests. By highlighting the importance of chemistry in everyday life, Mole Day helps to make science more accessible and interesting to everyone.