Question about number of weeks pregnant??

Kimberlygator

I just took a pregnancy test yesterday and it was positive.  I'm confused about how to calculate the number of weeks pregnant.  Some websites calculate from date of last ovulation and some from the date of the first day of last period. 

Date of last of ovulation was probably April 26th and date of first day of last period was April 12th.  So, do I say I am 2 weeks 4 days or 4 weeks 4 days? 

Also, when you talk about your first u/s at 8 weeks is that 8 weeks from ovulation or from date of first day of last period?

Thanks!

Thank you.