The arm pads of the goalie's chest protector should be able to move freely and fit comfortably in the cuff of the glove.
Although gloves are only sized from Youth to Senior, most companies offer a variety of different styles and features to choose from.
Recommendations
Senior ― 13 years and older
Intermediate ― 11 to 13 years old
Junior ― 8 to 11 years old
Youth ― 5 to 8 years old
Keep in mind that fitting a glove for a goalie is largely determined by personal preference rather than standard measurements.