Method for estimating a gas flow in an enclosure maintained in a low pressure regimen relative to the gas, including: measuring, as a function of time, a gas flow Jmeasurement in the enclosure, and estimating values of the parameters A and B iteratively implemented by decreasing an estimation error based on a difference between Jestim(t) and Jmeasurement, and wherein, when Jmeasurement corresponds to a pressure rise of the gas in the enclosure, Jestim(t) is calculated according to the equation: J estim ⁡ ( t ) = 2 ⁢ A ⁢ ∑ n = 1 n ⁢ ⁢ ma ⁢ ⁢ x ⁢ ( B π ⁡ ( t - OffX ) ) 1 2 ⁢ exp ⁡ ( - 2 ⁢ ( n + 1 ) 2 4 ⁢ B ⁡ ( t - OffX ) ) + OffY and when Jmeasurement corresponds to a pressure decrease of the gas in the enclosure, Jestim(t) is calculated according to the equation: J estm ⁡ ( t ) = P init - 2 ⁢ A ⁢ ∑ n = 1 n ⁢ ⁢ ma ⁢ ⁢ x ⁢ ( B π ⁡ ( t - OffX ) ) 1 2 ⁢ exp ⁡ ( - ( 2 ⁢ n + 1 ) 2 4 ⁢ B ⁡ ( t - OffX ) ) + OffY FIG. 1.