How to estimate the due date yourself?

I just recently found out that I am pregnant I haven’t visited any doctors or made an appointment yet because I figured I’m only like 4-5 weeks since I just missed my period. I’ve been reading online some information but I thought I would ask here. Did anybody else try to calculate their due date when they found out they were pregnant and how?

No hate comments or anything negative. I’m new to this and I’m needing all the advice I can get.