Scaling laws predict global microbial diversity. Kenneth J. Locey and Jay T. Lennon analyzed global microbial and macrobial data to show that commonness and rarity scale similarly across microorganisms and macroscopic plants and animals. They identified a universal dominance scaling law that spans 30 orders of magnitude, predicting the abundance of dominant ocean bacteria. Combining this law with the lognormal model of biodiversity, they estimate Earth hosts up to 1 trillion microbial species. Microbial biodiversity is greater than previously thought but predictable from the smallest to largest microbiomes. The study highlights the importance of scaling laws in understanding biodiversity across all life domains. It also emphasizes the need for continued research and collaboration to catalog Earth's microbial diversity, as current data and methods are insufficient to fully capture the complexity of microbial ecosystems. The findings suggest that microbial communities are exceptional in their rarity and unevenness, driven by unique biological traits. The research provides a framework for predicting microbial species richness and understanding the distribution of abundance across different scales. The study underscores the significance of scaling laws in ecology and biodiversity theory, offering a unified approach to predict diversity, commonness, and rarity across all scales of abundance.Scaling laws predict global microbial diversity. Kenneth J. Locey and Jay T. Lennon analyzed global microbial and macrobial data to show that commonness and rarity scale similarly across microorganisms and macroscopic plants and animals. They identified a universal dominance scaling law that spans 30 orders of magnitude, predicting the abundance of dominant ocean bacteria. Combining this law with the lognormal model of biodiversity, they estimate Earth hosts up to 1 trillion microbial species. Microbial biodiversity is greater than previously thought but predictable from the smallest to largest microbiomes. The study highlights the importance of scaling laws in understanding biodiversity across all life domains. It also emphasizes the need for continued research and collaboration to catalog Earth's microbial diversity, as current data and methods are insufficient to fully capture the complexity of microbial ecosystems. The findings suggest that microbial communities are exceptional in their rarity and unevenness, driven by unique biological traits. The research provides a framework for predicting microbial species richness and understanding the distribution of abundance across different scales. The study underscores the significance of scaling laws in ecology and biodiversity theory, offering a unified approach to predict diversity, commonness, and rarity across all scales of abundance.