What is the relationship between cardiac output and heart rate?

Cardiac output is the volume of blood pumped by the heart in a minute. Heart rate is how many times you heart beats in a minute. So the more your heart beats in a minute, the more volume it moves during that minute, and the higher you cardiac output will be. If you want to find out cardiac output, you need to multiply the heart rate and the stroke volume. The stroke volume is the volume of blood your heart moves per beat. Hope this helped.