Dry Malt Extract (DME) gives about 46 gravity points per pound per gallon of water. That means one pound of DME in one gallon of water has a gravity of 1.046. Liquid Malt Extract (LME) give about 35 gravity points per pound per gallon.
If you run the numbers, a pound of DME in 5 gallons will give you 9.2 gravity points. A pound of LME will give you 7 points in the same 5 gallons.
Your best bet is to use DME. It's a much more consistent product and stores very nicely, so you don't have to use the whole bag. Just store the excess in a zip lock bag in the refrigerator.