So I'm on a Mac and therefore don't have PokerTracker. But I've decided to track how many hands I play each session and compare that to my winrate, so that I can try to figure out what my BB/100 is.
I'm not the biggest math brain, so check my work here and see if this is right..

1) Divide money earned by BB.
For example, at NL10, if I make $7, 7/.1=70. So I know I've made 70 BB
2) Divide number of hands played by 100.
Ex. If I play 168 hands, I get a [insert math term here] of 1.68
3) Divide #BB earned by that number.
Ex.Divide 70 BB by 1.68. I get 41.66BB/100. Highly sustainable IMO

Also, if the total number of hands played < 100, unlike above, what do I change? Instead of dividing hands played by 100, would I divide 100 by number of hands played?

Thanks

yeah looks about right

nothing

In terms of the math, "nothing" is indeed correct. However, you shouldn't even bother calculating BB/100 for small samples. You need to throw your results into excel/spreadsheet-of-your-choice after each session, and run the math on the totals. If you want the stats for a time period shorter than lifetime but longer than a session, select the period you want and plug in those subtotals.

Excellent point. Not sure why I was even worried about that.

just a note I'd like for clarification, in pokertracker is BB/100 big blind or Big Bet ie 2* bb

by default it's big bet
you can change it on preferences tab if you like

this maybe an absolutely n00b question, but when you say 'hands played', does that mean hands dealt to you, or does it mean hands that you actually saw flop or voluntarily put money in?

so if i get dealt cards and limp, someone raises and i fold, did i play the hand?

It's every hand you're dealt, even if you fold without putting money in the pot.