Everyone's heartbeat is different! Our hearts beat to push blood through our bodies, and everyone's body is different. Most kids your age have a heartbeat between 70 and 110 beats every minute. Our heart rates also change throughout the day. If you exercise your heart rate can go up to 200 beats every minute! It can't stay that high for very long though, so when we rest our heart rate comes back down to normal. You can ask an adult to show you how to measure your heart rate by touching your wrist or neck and find out how many times your heart beats in one minute!!
A mammal's heart will beat for between one and three billion heart beats over its lifetime. Since human hearts beat at between 50 and 90 beats per minute, approximately, this means a lifespan of between 30 and 100 years (humans have lifespans in the upper part of that range, closer to three billion heartbeats than one billion).