What percentage of Earth history is represented by the Precambrian?

The Precambrian encompasses the vast majority of Earth's history, lasting from the formation of the Earth about 4.6 billion years ago until approximately 541 million years ago, when the Cambrian Period began. This expansive time frame includes about 87.5% of the Earth's geological history, which is significant compared to the much shorter duration of the Paleozoic, Mesozoic, and Cenozoic eras collectively known as the Phanerozoic Eon.

This extensive period is marked by critical developments in Earth's formation, the establishment of the early atmosphere and oceans, and the emergence of the first simple life forms. Understanding that the Precambrian represents such a large portion of Earth's history underscores its importance in geological and biological evolution, providing a foundational context for everything that follows in later geologic time periods.