A system and method are provided for estimating the operating speed of a turbocharger. A first pressure value corresponds to pressure at or near the air inlet of the compressor, and a second pressure value corresponds to pressure at or near the air outlet of the compressor. A temperature value corresponds to a temperature at or near the air inlet of the compressor, and a flow rate value corresponds to a flow rate of air entering the air inlet of the compressor. The operating speed of the turbocharger is estimated as a function of the first pressure value, the second pressure value, the temperature value and the flow rate value.