A respirator (1) includes a fresh gas port (23, 25, 27) for connecting a fresh gas supply, a gas outlet (3) for connecting a supply line for a patient, an absolute pressure sensor (21) and a data processor (37). The gas outlet and the fresh gas port are fluidically connected via an inhalation branch (17) that is connected to the absolute pressure sensor. The fresh gas port has an adjusting valve (31), to set gas flow from the fresh gas supply to the inhalation branch, and a differential pressure sensor (33). The differential pressure sensor determines a differential pressure in the fresh gas port between the inhalation branch and the adjusting valve. The data processor receives and records the absolute pressure measured and the differential pressure to determine a fresh gas flow through the fresh gas port. A method for determining a fresh gas flow is also shown and described.
