You can do a due date calculation on the nhs website. Just type in due date calculator into google and it’ll pop up. You add the first day of your last period and the length of your cycle for it to give you a more accurate date
They use baby’s head size as dating so it’s pretty inaccurate if you have a little one with a big head!
I think initially yes but then your 12week scan gives you official due date based on baby size