Abstract: A portable loose-leaf material vaporizer 1 comprises a heating chamber 20 for housing loose leaf material and vaporizing one or more active agents from the loose-leaf material, a mouthpiece 3 for withdrawal of the one or more active agents vaporized from the loose-leaf material, and a processing unit. The processing unit is configured to control temperature of the heating chamber 20 and to estimate a dosage of the one or more active agents withdrawn from the vaporizer 1 based on a mathematical model. The mathematical model relates vapor generating time and loose-leaf material properties, and optionally temperature of the heating chamber 20, to the dosage of the one or more active agents withdrawn or to be withdrawn from the vaporizer 1.