How to find the torque on a sprocket?

I have a 1/2 hp dc motor, putting out 100 rpm on the shaft, nameplate says 320 in lbs of torque, it has a 60 tooth sprocket on it(7"dia), from there it drives a15tooth sprocket(1.75"dia). I want to know what is the torque on the small sprocket and how would I increase it?