IPv6 Maths - See the Big Picture Experts tell us that IPv4 would generate 4,294,967,296 possible IP addresses. In practice it turned out there were only about 17 million useful addresses . With the 128bit IPv6 addresses, the same experts say there should be 340,300,000,000,000,000,000,000,000,000,000,000,000,000 IP addresses. However, there may be as few as: 18,000,000,000,000 useful IPv6 addresses. This shortfall is partly due to reserved and unassigned bits in the 128bit address. The other reason for this reduced number of usable IP addresses is a design feature whereby 64-bits are taken up with the Interface ID (Mac Number). Even with this surprisingly low estimate, it still means that everybody on the planet could be given 3,000 IP addresses. One day, we could see one IPv6 for the computer, one for the phone, car, fridge, cooker and every other appliance - then some.