Abstract
Calorimetry is the best technique available to perform absolute measurement of absorbed dose. Graphite or water calorimeters are mainly used as reference for absorbed dose in water in most of the national metrology laboratories involved in ionizing radiations. LNE-LNHB has a long experience with graphite and tissue-equivalent calorimeters. Graphite calorimeter is nowadays the reference dosimeter for photon and electron beams at LNE-LNHB. Associated with a transfer procedure from graphite to water, it leads to the reference of absorbed dose to water which is the reference quantity for radiotherapy. A water calorimeter is being developed currently in order to compare different ways to establish the standards of absorbed dose to water at LNE-LNHB.