Measure a baseball glove by extending a flexible tape measure from the top of the index finger to the bottom of the heel while making sure the tape measure touches the glove at all times. Both field and first base gloves are measured using this method. However, catcher's mitts are measured by extending a flexible tape measure around the glove's circumference.
The size of a baseball glove is based on the position for which it is intended. Outfield gloves are large and have extra finger support with a long and deep design to help with fly balls and diving catches. Infielder mitts are small and designed for quick technical plays, such as a double in the middle infield. Infielder mitts are equipped with a wide and shallow pocket so the fielder can get the ball out of the glove quickly.
Pitcher's gloves are large and do not have as much padding as regular gloves, as they are instead built for comfort. Pitchers need extra room in their gloves to hide their hand movements from the batter. Catcher's mitts are very large, come with extra padding and do not have separate openings for fingers, allowing catchers to catch fastballs for an entire game. First base gloves are a cross between regular gloves and catcher's mitts. A first base glove is larger than a regular glove, but has less padding than a catcher's mitt so as to remains flexible and useful in scooping bad throws off the ground.