# How to convert size represented in one prefix length to another?

Example, let's say if someone says, I have allocated one `/64` address. How can I convert that to a size in `/30`? How many `/30` equals to one `/64`?

• Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer. – Ron Maupin Dec 14 '19 at 21:21

How can I convert that to a size in /30?

This question does not actually make sense.

How many /30 equals to one /64?

Neither does this question make sense.

I assume you mean IPv6 because there is no such thing as an IPv4 `/64` network.

Your last question could make sense if you reverse it to ask how many `/64` networks can be made from a `/30` prefix. The way to calculate that is to subtract 30 from 64 to get 34. The answer would be 2 to the power of the result.

``````64 - 30 = 34
2^34 = 17,179,869,184
``````

That means you can derive 17,179,869,184 `/64` networks from one `/30` prefix.

For IPv6, you will probably divide your `/30` prefix into `/48` (or shorter) prefixes to assign each site a `/48` prefix. That means that you can have 262,144 sites, each with 65,536 standard IPv6 `/64` networks.

The reason to use `/48` (or shorter) for each site is that is the longest prefix that the ISPs will advertise on the public Internet.