Motorola often uses a bandwidth calculator with its operator customers to determine what bandwidth they need to deliver to subscriber homes. The calculations involve numbers like service uptake percentages and concurrency rates (i.e. the number of concurrently active subscribers expected).
If you’re not into that level of detail, consider instead the chart below (click to enlarge) on how much bandwidth specific applications require. Motorola’s Jeff Walker presented the chart in a discussion of TelcoTV at, ironically, the Cable IPTV show. This chart focuses specifically on DSL delivery using MPEG4 video compression. With fiber, the bandwidth number almost doubles because it’s possible to forego video compression. No video compression means higher video quality.
How much bandwidth will you need in a few years?