A centrifugal fluid pump assembly 1 includes a body section 5 and a control mechanism 6. The body section 5 includes a housing 20, an impeller 21 rotatable within the housing 20, and a motor 34 for rotating the impeller 21. The pump assembly 1 includes a motor current flow rate-related data storage section 60 for storing, for a plurality of different predetermined viscosities, predetermined viscosity-related flow rate data formed from a plurality of motor current flow rate relation data at a plurality of different impeller rotational speeds at predetermined fluid viscosity, a fluid measurement data inputting section 57, an impeller rotational speed measurement function, a motor current measurement function, and a flow rate calculating section 58 for using a fluid viscosity value, an impeller rotational speed value, a measured motor current and data stored in the motor current flow rate-related data storage section 60 to calculate a fluid flow rate. <；IMAGE>；
