National Mole Day

Celebrated on 10/23/2026

Quick Fact

National Mole Day celebrates Avogadro's Number (6.02 × 10^23), a fundamental constant in chemistry. It is observed annually on October 23 from 6:02 AM to 6:02 PM, reflecting the number's first digits. The holiday was inspired by a teacher in Wisconsin who wanted to make chemistry fun.

Origins and Establishment of National Mole Day

National Mole Day was founded in 1991 by a high school chemistry teacher named Margaret (Marge) Christensen in Prairie du Chien, Wisconsin. She aimed to create a fun, educational event that would spark students' interest in chemistry by celebrating Avogadro's Number. The date October 23 was chosen because in the American date format (10/23), it resembles 6.02 × 10^23, and the time 6:02 AM to 6:02 PM further emphasizes the number.

Evolution and Modern Commemoration

Initially a local classroom activity, National Mole Day gained popularity through the National Mole Day Foundation, which Christensen established. Today, it is celebrated in schools and chemistry clubs worldwide. Activities include mole-themed puns, contests, and experiments. Some schools hold "mole day" events with mole-shaped cookies, while others organize scavenger hunts or create giant models of Avogadro's Number. The day has also expanded to include online resources and virtual celebrations.

Facts & General Observations

• Avogadro's Number is named after Italian scientist Amedeo Avogadro, who proposed in 1811 that equal volumes of gases at the same temperature and pressure contain the same number of molecules.
• One mole of any substance contains 6.02214076 × 10^23 elementary entities (atoms, molecules, ions, etc.). This number was redefined in 2019 to be exactly that value.
• The National Mole Day Foundation estimates that over 10,000 teachers and students participate in organized mole day events each year in the United States alone.

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