Class D airspace has no "layering" like that of the upside down cake pattern like in B airspace. Therefore it is usually a circle of a 4NM radius around the central airport. Typically as stated above it reaches roughly 2500AGL (translate that to MSL - should be on your sectional) then typically it is echo above to 5,000 MSL HOWEVER some D airspace is underneath other types of controlled airspace. For example there may be a couple hundred feet of the Echo above the class Delta ceiling however above this E airspace possibly a Bravo (class B) is present. A look at the sectional and the Legend will entail the details of your situation! Good Luck