You need to do load testing to determine this - a request's time includes many delays that are not related to the work the server does, and thus it's not as simple as 1/0.03 - it's possible that 0.0001 second of that time is actually server time, or 0.025 - plus you also have to consider if there are multiple cores working, or non-linear algorithms running, or who knows what else.

Best way to figure it out is to use an application like Apache Bench from a powerful computer with a good internet connection, throw a lot of concurrent connections at the site, and see what happens.