Are 4 pounds of fingerling potatoes enough to feed approx 25-30 people? I'm going to be cutting them in half.

I agree with thirschfeld, 4 oz pp would be my plan.
Good Luck
irina

I had 20 people over last weekend and I served 4 lbs. of potatoes as part of a buffet and I had plenty of leftovers.

As part of a meal you can usually figure 4 oz serving size per person and that is if it a group of heavy eaters. It also depends on what else is being served. If it is buffet with another starch then you have plenty.