how accurate is dating scan

if you can’t go off lmp bc it was a month prior to you conceiving(based on due date) how accurate was dating scan for you ? i am always paranoid they gave me the wrong due date and measurements but i heard that it’s more accurate than lmp especially for someone like me with irregular periods. all my other ultrasounds they never said anything about me being too far ahead or behind so i guess that means original scan was correct?