Bay windows have three window sections that form an angular projection, while bow windows often have more than three windows and form a curved area. Bay windows typically have one large window in the middle with two smaller windows on the sides. The individual sections in a bow window are generally all the same size.
The angular shape and three panels of a bay window means it typically sticks out farther than a bow window. This also means more floor space below the bay window on the inside of the home. Typical angles for bay windows are 90 degrees, 135 degrees or 150 degrees from the house. The larger window in the middle of a bay window typically offers one large piece of glass with no obstructions for a wide outside view.
The typical bow window has four or five individual windows connected to create the curve. Bow windows are generally wider than bay windows because they curve gradually. Because they use multiple window panels, bow windows can go around the corner of a home to create a turret-style shape. While bow windows have more glass and may allow more light into the space, the multiple window panels also mean more separations in the glass. This can slightly obstruct the view to the outdoors.