I don't convert to DNG very often. Most of the time I prefer working with the original raw files. So my observations may not be 100% accurate. The size of the DNG files can vary depending on the options you choose. For instance, including fast load data seems to add slightly to the size of the file. And, are you embedding the original raw file? That can affect the size of the file as well. So how are you setting up your options?
In answer Jimitess above, I try to keep my file low by selecting in RAW preferences, 1. "No JPG preview" and 2. "don't embed original RAW file".
I teach Photoshop and RAW and need DNG files to communicate with students. Other photographers have RAW files of typically around 14 Mb. Mine are more than 4 times as large.
Have downloaded the DNG codec several times as for some reason is slows my download time from sd card to a snails pace.One instance I timed downloading 32 12 mp files at 7 minutes which would make the time redicioulsly long.will download again and change the setting to 'embed origional raw files' and see if that helps