An apparatus and method is disclosed for calibrating a cup anemometer having a non-removable cupset. The calibration method may include mechanically connecting a cups assembly hub of the anemometer to a rotatable shaft of a variable-speed motor, placing at least the anemometer under vacuum so that drag effects on the cups assembly hub of the anemometer are eliminated when driven by the variable-speed motor, controlling the variable-speed motor to drive the cups assembly hub of the anemometer at a number of different rotational speeds, recording electrical signals produced by the anemometer at each of the number of different rotational speeds, and generating calibration data for the anemometer based on the recorded electrical signals and on expected wind speed values at each of the number of different rotational speeds.