To choose the proper size for your umbrella, you need to determine what you'll use it for. Umbrellas have a few basic measurements. The umbrellas' diameter is the distance from one edge to the opposite edge across the bottom. The arc is the distance from one edge to the other over the top of the umbrella. The height of the umbrella is measured from the bottom of the handle to the top of the umbrella at the center peak. A personal rain umbrella typically has a diameter between 21-25in. A child's umbrella is smaller, usually measuring 11-19in. A golf umbrella is larger, so it can protect the golfer and his clubs. A golf umbrella is usually 25-34in in diameter. If you're purchasing a patio umbrella, select one with an extra two feet of coverage beyond each side of your table or seating area.