which performance counters for total mem and sql used mem?

hi there..
was hoping someone could help me.. what I was trying to do was using the performance counters in perfmon was to see total memory available on the box, along with how much is currently being used by sql server.
With this information I'd like to calculate some metrics like total percentage used etc, which I can do just fine on my own.. just not sure what performance counters I would use to show each of those values.
Any help would sure be appreciated.
Thanks