The government of Indonesia is committed to reducing carbon emissions through the Forestry and Other Land Uses (FOLU) Net Sink scheme, e.g., by measuring and calculating potential aboveground carbon in PT KOJO’s forest. This research aims to measure biomass and aboveground biomass in PT KOJO’s forest, Pinggir District, Bengkalis. Non-destructive sampling was applied by making plots of 20 m × 20 m (trees), 10 m × 10 m (poles), and 5 m × 5 m (saplings). Destructive sampling was carried out in a plot of 1 m × 1 m for seedlings and understory plants. Results showed that potential carbon stock at tree, pole, sapling, seedling, understory plant, litter, and necromass levels were 160.62 tC/ha, 34.60 tC/ha, 20.88 tons/ha, 1.54 tC/ha, 11.59 tC/ha, and 1.47 tC/Ha, respectively. The total carbon stock in PT KOJO’s forest was 160.69 tC/ha. Carbon stock in PT KOJO’s forest is classified as medium, therefore efforts are needed to increase carbon stocks and efforts to protect PT KOJO’s forest area so that stored carbon is not released into the air.