A calorie is fundamentally a unit of energy, and in the context of human physiology, the term refers to the kilocalorie (kcal). The question of how many calories a person burns in an hour is complex because this energy expenditure is not a fixed value. It is highly variable, depending on a person’s underlying metabolism and the specific physical demands placed on the body. Estimating hourly calorie burn requires understanding both the static factors that govern baseline energy use and the dynamic factors related to physical activity.
Your Baseline Energy Consumption
Every person burns a minimum number of calories simply to sustain life, known as the Basal Metabolic Rate (BMR) or Resting Metabolic Rate (RMR). This baseline energy is used for fundamental processes like breathing, circulating blood, and maintaining body temperature. The BMR is measured under strict laboratory conditions, while the RMR is a less restrictive, more practical estimate that is typically about 10% higher.
The calories burned at rest are determined by several static, biological factors. Body weight is a primary determinant, since a larger body requires more energy to maintain its mass. Body composition also plays a significant role, as muscle tissue is metabolically more active than fat tissue. Individuals with a higher percentage of lean muscle mass will have a higher baseline burn.
Age is another factor, with the metabolic rate generally decreasing as a person gets older, often due to a reduction in muscle mass. Hormonal factors and sex also influence this rate; men typically have a higher RMR than women because they naturally carry a greater proportion of muscle mass.
How Activity Intensity Determines Calorie Burn
Beyond the resting metabolic rate, the calories burned during activity are primarily determined by the intensity of the work performed. Scientists use the Metabolic Equivalent of Task (MET) to quantify this intensity. One MET is defined as the energy expenditure of sitting quietly at rest, roughly equivalent to burning one kilocalorie per kilogram of body weight per hour.
Different physical activities are assigned specific MET values based on how much oxygen the body consumes compared to the resting state. For example, an activity with a MET value of 5 requires five times the energy expenditure of sitting still.
The MET value, combined with a person’s body weight and the duration of the activity, allows for the calculation of an estimated hourly calorie burn. The formula multiplies the MET value by the body weight in kilograms and the time spent in hours. This calculation yields the gross energy expenditure, which includes the calories that would have been burned anyway while at rest. The higher the MET value, the greater the hourly calorie expenditure will be.
Estimated Calorie Burn for Common Activities
To illustrate how intensity translates into calorie expenditure, we can look at estimated hourly burn rates for a person weighing approximately 155 pounds (70 kilograms). These figures represent the total calories expended, including the baseline RMR, and serve as a comparative benchmark.
Activities classified as light intensity, such as sitting quietly at a desk or slow walking (around 2.0 mph), have low MET values and a modest hourly burn. A person weighing 155 pounds might burn about 110 to 140 calories per hour performing these low-effort tasks.
Moderate-intensity activities, which slightly elevate the heart rate and breathing, show a significant increase in hourly calorie expenditure. Brisk walking (3.5 mph), general yard work, or swimming laps at a moderate pace fall into this category. For the same 155-pound person, brisk walking for an hour might burn around 350 to 370 calories, while moderate-paced cycling (12–14 mph) could reach approximately 560 calories per hour.
Vigorous-intensity activities, which involve a sustained, high level of effort, result in the highest hourly calorie burn. Running at a pace of 6 miles per hour (a 10-minute mile) can lead to an expenditure of about 700 calories per hour for a 155-pound person. Similarly, high-impact aerobics or playing a competitive sport like basketball can push the hourly burn well past 600 calories.