Canarium tree as a source of food, energy, health and cultural development has been widely discussed but not in terms of biomass content. In general, studies have not been carried out properly regarding its ability to provide environmental services, especially in dealing with climate change. Therefore, this study aims to determine the value of Biomass Expansion Factors (BEFs) and Root to Shoot ratio (R/S). Beside that, to determine the allometric equation for young Canarium to be used in dealing with climate change. This is done through the Monitoring Reporting and Verification (MRV) System under the United Nations Guidelines for Reducing Emissions from Deforestation and Degradation (UN REDD). There were 32 young canaries at seedling and sapling levels aged 9-21 months in the nursery area, with a diameter of 3.4 - 4.9 cm and a height of 1.32 - 2.48 m. Before determining the allometric equation, the classical assumption test is carried out first. Young canaries have R/S value 0.52 and BEF values 1.50. The allometric equation is Y1 = -700,200 + 209.149X1 + 3.922X2 where Y1 = biomass above ground level, X1 = diameter, X2 = height with R squared 0.386. To calculate the total above and below-ground biomass simultaneously, the following 3 steps were carried out: (1) Calculating above-ground biomass using the allometric equation Y1 = -700,200 + 209.149X1 + 3.922X2, (2) calculating below-ground biomass by utilizing R/S value 0.52 and (3) summing above and below-ground biomass.