The study appraised rubber tree plantations at Bandarbans Hill Tract in Bangladesh, to measure the biomass in plantations of different ages and to determine the organic carbon content and CO2 equivalence.The DBH and biomass growth were increased with the age of the plantations so as the carbon storage and carbon-di-oxide equivalence (CO2e). All of them were sharply increased upto 15th year from the beginning and become slower after 15th year. The average DBH, above-ground biomass, below-ground biomass, total biomass, carbon storage and carbon-di-oxide equivalence for rubber plantation were 15.15cm, 160.12 Mg ha-1, 27.41 Mg ha-1, 187.54 Mg ha-1, 93.97 Mg ha-1 and 344.14 Mg ha-1 respectively. The highest DBH (1.54 87cm ha-1 yr-1) and biomass (53.29 Mg ha-1 yr-1) growth were found between 10 to 15 years of rubber plantation where the average growth of DBH (1.01cm ha-1 yr-1) and biomass (23.71 Mg ha-1 yr-1). An average 11663.42 Tk ha-1yr-1 earn for rubber plantation in Bandarban hill tract only for keeping the tree in field. Three types of DBH based models were developed with strong mean R2 (Power = 0.99; Polynomial = 0.98 and Linear = 0.90) and all were highly significant (P < 0.05). The result will be explored the value of rubber plantation and helped the policy maker for advancing the management of forest in hilly area of Bangladesh.