The HP Engage One is equipped with a 15-inch display. This size is optimized for point-of-sale (POS) applications, providing a balance between visibility and compactness suitable for retail and hospitality environments. The 15-inch display allows for clear and efficient interaction with the system, whether for staff or customer-facing operations. This specific detail can be confirmed through the HP Engage One product specifications and user manuals, which provide detailed descriptions of the hardware components and features included with the device.