BMR stands for Basal Metabolic Rate. It is the number of calories that your body needs to perform basic functions like breathing, circulating blood, and maintaining body temperature while at rest. BMR is affected by various factors such as age, gender, weight, and muscle mass.

The BMR calculator is a tool used to determine the number of calories your body needs in a day based on your BMR. It helps in estimating the minimum amount of energy required to keep your body functioning properly. By knowing your BMR, you can better understand your body's energy needs and plan your diet and exercise accordingly.