With a diameter of 3,474 km, it is about 1/4th the size of the Earth. Translated into miles, that is about 2100 miles, which is about the size of the United States.
The volume of the Moon is 2.195 x 1010 km3, which is only 2% of the volume of the Earth. You could fit 50 Moons inside the volume of the Earth. The mass of the Moon is 7.347 x 1022 kg, which is about 12% of the mass of the Earth.
Sources:
Lisle, Jason. Taking Back Astronomy. Green Forest, AR: Master, 2006. Print.
"Size of the Moon." Universe Today. N.p., n.d. Web. 12 Oct. 2012. http://www.universetoday.com/20398/size-of-the-moon.