The invention relates to a measuring method for determining the recirculation rate (RR) in the anode gas circuit (50) of a fuel cell system (1) with fuel cell (10), wherein an anode gas (52) from an anode chamber (13) is supplied to the fuel cell (10) by means of a gas conveying device (70) via an anode gas recirculation line (51) and thermostated in an anode gas heat exchanger (60) arranged in the anode gas recirculation line (51). The following method steps are carried out for this purpose: measuring a first differential pressure loss (ΔP1_2) along a first line section (101) of the anode gas recirculation line (51) through which a first mass flow (M1_2) flows in the operating state of the fuel cell system (1); measuring a second differential pressure loss (ΔP3_4; ΔP2_3) along a second line section (102; 103) of the anode gas recirculation line (51), which is being flowed through in the operating state by a second mass flow (M3_4; M2_3) of different size than the first mass flow (M1_2); calculating the differential pressure loss ratio (RΔP) by quotient formation from second (ΔP3_4; ΔP2_3) to first measured differential pressure loss (ΔP1_2); determination of the recirculation rate (RR) in the anode gas circuit (50) using a characteristic system curve (S) as a function of the respective calculated differential pressure loss ratio (RΔP).