Trunk dimensions

Hey everyone, my first post. I want to add a custom subwoofer box to the trunk of my 99 grand am. I will build it myself and need the dimensions of the trunk. I looked all over online and don't want to rely on my measurements alone. Thanks in advance dudes.

I do alot of custom installs and have found it is best to go with your own messurement. The one thing I can suggest on the box is dont make it to deep because of the angle to put it in is pretty much straigt up and down. I have done 5 so far and have picked up a few tricks. I have built a box for 4 10s and had little prob getting it in there. Let me know if you need more help.