The human heart is an amazing machine. During resting conditions, on average, the heart contracts (i.e., beats) 70 times per minute. Thus, the heart beats 4,200 times in one hour, 100,800 times in one day, 36,792,000 times in one year, and over a lifetime of 75 years, it beats 2,759,400,000 (2.7 billion times)! The heart's volume output (i.e., cardiac output) is also phenomenal. During resting conditions, on average, each ventricle pumps 4.9 liters (1.3 gallons) of blood every minute. Thus, each ventricle pumps 294 liters (77.7 gallons) of blood per hour, 7,056 liters (1,864 gallons) per day, 2,575,440 liters (680,359 gallons) per year, and over a lifetime of 75 years, 193,158,000 liters (51,026,945 gallons) of blood! As there are two ventricles, and the output of the left and right ventricles must be equal under healthy conditions, the total volume output of the heart is twice the numbers given. Test your basic knowledge of the human heart by taking this simple quiz.