Mangrove forest in Madura Island is a type of one, which influenced by seawater tide, freshwater, soil texture, and salinity. The potential vegetation is dominated by Rhizopora stylosa. Allometric is one of a method for estimating carbon stock in mangrove forest by multiplying plant biomass of area. This study was aimed to (1) determine plant biomass and carbon stock in mangrove forest (2) comparing biomass and carbon stock allocation between stem, root, necromass, and litterfall. The results showed that total biomass and carbon stock potential of Rhizopora sytlosa was 23477,09158 ton and 553,62730 ton/ha. Partitioning biomass was higher in necromass part about 88,88% of total biomass, meanwhile carbon stock allocation was higher in stem part about 88,36 % of total carbon stock. In contrast, there is nonsignificant correlation stem biomass and stem carbon stock. These trends in higher biomass allocation are not related to carbon stock allocation in a mangrove forest.