Question about m&m's

I'm just curious how I figure out how many lbs of M&M's I need. If they organza bags or tins I get are 1.7 ozs, then does this mean that I get 1.7 ozs of M&M's per guest? Or do I get less because I won't need to stuff it full???

Help me figure out how many lbs of M&M's I would need for 300 people!!!!