The invention relates to a method for measuring the flow rate of cooling air in a cooling air circuit (13) of a casing (121) of a high-pressure turbine (9) of a turbomachine (1). The invention is characterized in that sensors (21, 22, 24, 26, 28) are used to measure a total pressure at the fan inlet, a static pressure at the outlet of the high-pressure compressor (6), a rotational speed of the low-pressure shaft (101), a rotational speed of the high-pressure shaft (91) and a degree of valve opening of the cooling air circuit (13), a calculation unit is used to calculate the flow rate of cooling air on the basis of at least the measurement of these.