But that isn’t on the left side of your chest. It’s near the center, between the lungs. It angles slightly left, which is where you notice its beating. In most adults, the heart is about twice the size of a fist.

A normal heart beats about 100,000 times a day-35 million times a year. Assuming an average life span, your heart will beat between 2.5 and 3.0 billion times, pumping some 55,000,000 gallons of blood! An industrious little muscle indeed. About 6 quarts of blood circulate through your entire system every 20 seconds. Each 24 hours, that blood travels 12,000 miles. Your heart muscle uses about the same force to pump blood as you’d use to squeeze a tennis ball, which can squirt a stream of blood about 30 feet.

From: 20 Things You Didn’t Know by the editors of Discover Magazine and Dean Christopher.