Am I 4 weeks or 5 weeks?

dyg201

This is probably a dumb question, but I know I am 4w0d today, but FF pregnancy tracker calls this "week 5."  So if I was saying how far along I was, would I say 5 weeks?  I think that's how it goes

I have my first appointment on May 24th so I was wondering if I will be 6 or 7 weeks at that time.