By specifying a group of devices you need to protect, from a single workstation to an entire datacenter, the UPS selector will estimate your power requirements, allow you to specify your required runtime and other options, and recommend a single UPS solution.
Make sure the equipment you specify is in close proximity, as a UPS can only protect the equipment if the power cords can reach it. Equipment not in close proximity is considered another group. Use the UPS selector to find a solution for each group separately.