i want to perform manual capacity review

Hello

Can anyone let me know how to perform capacity review for ESX cluster by MANUALLY , i don't want to go for paid tool such as vkernel etc

I tried with alan script http://www.hypervisor.fr/?p=1890, but it gives something different value, I don't belive it is correct values

ClusterName                NumVmLeft[CPU]             NumVmLeft[MEM]
-----------                --------------             --------------
xxxxxx                    42 [513 Mhz]               2 [1802 MB]
xxxxxx          650 [51 Mhz]               6 [1627 MB]

So anyone knows calacution about performing manual capacity review greatly apperciated.

Thanks