If you have a child between 12-18 months, how many words do they have?

Our youngest is 16 months and she has maybe 10 words but repeats everything. I'm comfortable with where she's at, however it's hard since her sister was talking 3-4 word sentences at this age. (I know, don't compare, but it's hard not too!) I'm not worried at all, just interesting that they are so different. How many words does your LO have?