This study provides the first global estimates of fine root biomass, length, surface area, and nutrient contents, which are crucial for improving global biogeochemical models. Fine roots, defined as those ≤2 mm in diameter, play a vital role in water and nutrient uptake, carbon cycling, and nutrient cycling. The analysis includes data from 253 field studies and over 100 additional studies to estimate root distributions, biomass, length, surface area, and nutrient contents. The results show that fine root biomass ranges from 0.27 kg·m⁻² in deserts to 1.5 kg·m⁻² in temperate grasslands, with live fine root biomass at 0.13 kg·m⁻² and 0.95 kg·m⁻² in these biomes, respectively. The average C:N:P ratio in living fine roots is 450:11:1, and the global fine root carbon pool is approximately 5% of the atmospheric carbon pool. The global fine root surface area is estimated to be 2.0 × 10⁵ km², four times the surface area of Earth. These estimates highlight the importance of fine roots in global biogeochemical processes and provide a benchmark for improving models of carbon and nutrient cycling.This study provides the first global estimates of fine root biomass, length, surface area, and nutrient contents, which are crucial for improving global biogeochemical models. Fine roots, defined as those ≤2 mm in diameter, play a vital role in water and nutrient uptake, carbon cycling, and nutrient cycling. The analysis includes data from 253 field studies and over 100 additional studies to estimate root distributions, biomass, length, surface area, and nutrient contents. The results show that fine root biomass ranges from 0.27 kg·m⁻² in deserts to 1.5 kg·m⁻² in temperate grasslands, with live fine root biomass at 0.13 kg·m⁻² and 0.95 kg·m⁻² in these biomes, respectively. The average C:N:P ratio in living fine roots is 450:11:1, and the global fine root carbon pool is approximately 5% of the atmospheric carbon pool. The global fine root surface area is estimated to be 2.0 × 10⁵ km², four times the surface area of Earth. These estimates highlight the importance of fine roots in global biogeochemical processes and provide a benchmark for improving models of carbon and nutrient cycling.