Toddler vocabulary?

My son just turned 18 months old and i am wondering if a child’s vocabulary consists of just the words he/she actually can speak or if you include all of the words that you know he/she understands as well. He can understand well over 150 words (i have a list going with 170 on it now, and i remember new words he knows everyday) but he can regularly speak and use about 100 words, some in short sentences (its hot, where did it go?) Does anyone else count their vocabulary with all the words they understand? And is he on track for his age, this is my first so I’m not too sure what’s “Normal”