Baby measured a week ahead

Hi! This might be a silly question but I had my 12 week ultrasound/first trimester screening on Monday. When they measured the baby s/he was measuring 13 weeks and 2 days even though I am only 12 weeks. Sooooo does that mean I am actually 13 weeks pregnant or am I still 12 weeks pregnant haha??? Like did I skip an entire week? Just trying to decide what to tell people when they ask how far along I am because I was going to start announcing to friends!

Would you still say 12 or switch to 13?