A method and apparatus for calibrating a temperature sensor is disclosed. In one embodiment, a method comprises generating first and second digital values based respectively on first and second voltages applied to a portion of a temperature sensor circuit. An arithmetic circuit may derive the value of the second voltage based on the first and second digital values. The method further comprises determining an initial value of a constant based on values of the first and second voltages, and determining a final value of the constant based on the initial voltage and at least one voltage offset. The constant may then be used in determining temperature readings for the temperature sensor.