Hello!
Have you considered having a contract service come in a perform this? That is their business, and they are usually quite familar with the classifications and the documentation. That may give you a start. This is NOT to suggest that you are not competent, or you can't do your own test. It just sounds like you may be getting down to 'crunch time'. The money spent (given you pick a good certification company) will be well worth it to give you a start. Too, if you are seeking some industry approval, using a reputable certification organization may be a plus.
1. Are you just testing the room for particle classification, or do you have HEPA filters you are also going to test? Filters are another fun ballgame.
2. Did you build your own cleanroom, or did someone build it for you? If someone built it for you, they should have given you some documentation to support the classification.
3. If you built it yourself... NOTE: Without making modifications, the room will be what it is. It may or may not meet your specifications.
As far as the calculations, most of the more current particle counters already have printouts/algorithms to present the criteria for the classifications. As Marc pointed out, you really should purchase the copy of the specification.
Also, particle testing should occur while activity is being conducted in the room, to simulate the actual generation of particles.
Just some thoughts. Good luck, and repost if there are more questions.